being delicate flamingo mom is suffering
Bio data tells us Shizuma is 184cm, 62kg and he has a Virgo birthday of September 28th. He has waist-length pink hair usually tied up, and clear grey eyes. You can see his official page and some voice samples here.
Here's stuff from some of his official profiles.
怜治の幼なじみで、付き人のようにいつもそばでサポートをしている。物腰が柔らかく、Overall he speaks in keigo (polite Japanese) and addresses everyone properly without affectionate name suffixes. His first-person pronoun of choice is watashi, and he calls Reiji Reiji-sama. In private, however, he drops the -sama and uses casual Japanese. His pronoun also changes to ore.
Shizuma is Reiji's childhood friend and practically his attendant, supporting him at every occasion. He is a gentle person and acts as the mediator for the group. He is the performing leader for Galaxy Standard. (Reiji is the center and overall leader.) Manga vol. 2 mentions that he acts like Reiji's butler (which Nana also points out in the game) and that he's scary when angry. Vol. 3 tells us that he's been supporting Reiji since they were tinies and that they're perfect partners.
In the 'Characters' Opinions' section, Hozumi calls him 'Saisei's Mother Hen' and generally everyone either comments on his perfect Relationer work or his responsible nature. Riku even questions if he's actually a highschooler.
He's not the most athletic of people, but still has enough stamina and physical ability to perform concerts. However, it's acknowledged that he's no way close to the actual Saisei runners.
One of the main miffs I have about this game is that a lot of Reiji's (and by extension Saisei's) backstory is left kind of vague. Maybe we'll see details, maybe we'll see some more in the Saisei Side manga serial/the light novel as it goes on.
Shizuma's family, the Mayuzumis, are the Suwa family's gardeners. Reiji's folks are Japanese dancers and open a school for it. Since they're very good (it's probably a family trade) they are also super rich so they can afford an estate (built in the old Japanese style, probably a very old building) and at some point they hired gardeners. Shizuma is a year older than Reiji, who is in turn a year older than the younger Mayuzumi (Asuma) so they grow up together as childhood friends. Asuma has a very shounen and blunt personality, which is a huge contrast to the soft-spoken Shizuma. As an older brother, he ends up mothering/telling off his younger sibling quite a few times.
The three of them attend school together and do sports together, the usual. At some point Reiji and Asuma got interested in Stride, so Shizuma gets dragged/invited along to practice in the sport. We don't get details about how they fare in middle school, but somewhen during that time Shizuma gets injured in an accident and becomes wheelchair-bound. This incident also led to him repeating one year of school, thus he is in the same year as Reiji and is a year older than the other people in his class. We don't get details on what exactly it is, except that Reiji was implicated/partially the reason why Shizuma gets injured so it could very well be a heroic sacrifice kind of thing. It's not a permanent injury, though - he had rehab after that, and when they entered high school he could walk again.
Saisei High School has its original campus in Kamakura in Kanagawa Prefecture, which is where Reiji and Shizuma originally live in. However, they ended up spending time in the satellite campus in Roppongi, Tokyo, which houses Saisei's performer's division. Reiji joined the Stride team in his first year, and Shizuma followed in as the team's Relationer. Both of them are also members of Saisei's own idol unit, Galaxy Standard. The unit is quite popular, mostly thanks to Reiji's
It's stated in the game that the Saisei team is one of the strongest ones, owing to the quality of their runners as well as Shizuma's ability. The school is also extremely well-equipped with facilities - basically, it's a top-tier high school
Here's where the game sort-of veers in towards 'unrealistic shounen sports' territory. Shizuma is some kind of a telepath - which is attributed to why he's a very good Relationer, in the sense that he can speak to his team mentally instead of having them waste breath to talk, as well as sense the strongest feelings of his teammates and opponents. He is shown only to converse one-on-one with Reiji, but has the sensitivity in its base form. This ability is only shown during races, and it's implied that it is quite commonplace in people who choose to train as Relationers. Nana and Toya are both shown to have this ability, as well as Nana's mother.
Mostly game things from Reiji's route. Some Saisei Side stories are in the manga, however - so far, they are before the route split only (but I haven't bought Vol 4 or 5 yet so that might change).
We first meet Shizuma when the Hounan team first sign on to their modeling contract. Nana leaves her phone unattended outside the studio, and Reiji ends up picking it up. Reiji asks Shizuma about the charm on Nana's phone, and he tells him that it's a mascot from Hokkaido - Melonko-chan. When Reiji comments that Shizuma seems to know everything, he just replies that it's in preparation for anything that Reiji might ask. They return to Nana after she goes out in search of it. When Reiji expresses interest in acquiring the item, Shizuma assures him that he will help in looking for it the next time they go to Hokkaido. The two then leave for their assigned studio, leaving Nana to go back to her team.
Later on the Saisei team appears again during the Trial Tour at Nasushiobara City. They board the same train as the Hounan team, except in a special First-Class carriage. Nana wanders into the carriage in search of the washroom, and receives an accidental water-bottle-to-the-head courtesy of Asuma. Shizuma apologizes on his brother's behalf, and he is able to name her accurately as well as her school and role. However, they don't get to talk much before Heath comes to retrieve her. Later on, at the Tour site, Galaxy Standard performs for the opening ceremony before going for their Trial race.
While the Hounan team are facing off against the Nagamine team, the Saisei team watch the match. Asuma and Kaede go to the actual track, while the other four members stay behind. The remaining four talk about Hounan's revival and its status as one of the Original Four schools specializing in the sport, before Shizuma asks Reiji if he should make tea. Bantarou ends up impressed by Hozumi's save, and they start reconsidering Hounan's revival much more seriously.
When the Hounan team finally reach their onsen hotel that night, it also turns out that the Saisei team are staying over in the same hotel. The two teams spend some time together playing indoor sports and games - it's Reiji's idea for everyone to make friends with each other, which Shizuma helps to coordinate. The teams play doubles table tennis against each other, with Reiji and Shizuma scoring the decisive point in Saisei's favour. It's generally a fun occasion, but it's noticeable that Reiji reacts very positively to Nana and it sets the stage for much of the two teams' interactions.
Later on in May, Shizuma and Reiji run into Nana again at the modeling studio, where the latter asks her to talk to him if she has any problems. This leads to Nana seeking out the Saisei team after Ayumu gets injured during the Ichijoukan race - she makes her way into the school to see him. Reiji already knows about it thanks to Shizuma's information gathering. It's evident by now that Reiji has his eye out for her, even giving her his phone number - something that Shizuma notes and gets a little worried about.
In June, the two teams meet again at the modeling studio, and the conversation inadvertently turns to how the Hounan team is one short. As with before Reiji pays special attention to Nana, which Shizuma brings up to him later.
"If you have something to say, then say it. Keeping it to yourself is a bad habit."In July, the Hounan team loses to Kakyoin and as a result all the players are affected - especially Nana, who feels herself most responsible. Reiji pulls her aside to talk to her in private, and ends up confessing to her. When he returns, Shizuma doesn't keep quiet about it anymore.
"... you've been too friendly with the other school's relationer, and you don't realize. If you keep doing this..."
"Seriously, it's fine. Don't worry about me."
"[sigh] The more you say this, the more worried I get..."
"If you have something to say, then say it. Keeping it to yourself is a bad habit."Later on in the month, the Hounan and Saisei teams train together at a stay-over camp in the Kamakura main campus (again, it was Reiji's idea to invite them over). At Reiji's request, Shizuma teaches Nana about Relationers' telepathic abilities. We are shown in this chapter that Shizuma is careful and experienced enough with his telepathy to be able to discern exactly where and when the runners make small mistakes (starting, turning). After that, Shizuma helps Reiji coordinate the night camp activities. During the camp, Reiji ends up being turned down by Nana due to both of them having important sports duties. Even so, he recovers and they still keep in touch. All this, Shizuma is well aware of, and it doesn't make him any less worried.
"... so you listened?"
"[sigh] You didn't notice at all."
"Well, I know now. I did it on impulse. Did you think I was reckless?"
"... if that's the case, then you should correct it and tell her you weren't serious."
"Shizuma-kun, is that how you see it?"
"I'm helping her get over her loss. And - I was being serious."
We don't get to see much of the Saisei team in the next few scenes due to Hounan preparing for upcoming tournaments. Only in late July do they appear again - once more at the modeling agency. When Nana comes up to talk to Reiji, she gets interrupted by Shizuma before the conversation can get started.
"... Sakurai-san. Have you not realized yet?"Reiji then tells Shizuma that choosing to spend time with Nana is his own decision, and that he is well aware of the risks involved. Even if it was done with well intentions, he was overriding Reiji's own choices with his knowledge; and that Reiji had already taken precautions. Shizuma acknowledges his fault, but Nana already acquiesces and the two cut off meetings from then on.
"My most apologies, Reiji-sama. But - I need to protect you now. Sakurai-san. I know this is impolite of me to say this. However, you and Reiji-sama have differing circumstances. Please control yourself."
"Shizuma, what are you doing?"
"Reiji-sama is not only the one who works hard holds the Saisei Stride Team together, he also needs to fulfil his responsibilities as Galaxy Standard's main vocalist. He is also the only heir to the Suwa family, and he has to live up to that as well. You can imagine how heavy his duties are, can't you? Both of you are very close. If the mass media gets wind of this, then Reiji-sama's burden will only increase. Are you willing to bear the full responsibility in case this happens?"
"... Stop it."
"No, I will not. If anything happens, it will be too late. I am asking you to cease now. Reiji-sama is very busy, and he has collapsed before. There simply is no time nor energy left for him to spend on you. This is a very important time for him right now. You have different feelings for him as he does for you. Because of this, I ask that you stop bothering him."
"Shizuma, that's enough."
"Just stop. Please."
"... as you wish."
Time passes. The End of Summer (EOS) pre-party happens, where Nana's status is publicized and she gets hit on by some boys from the Tsubakimichi school. Reiji comes to her defense and the rest of the Saisei team follows. Kazuki, the lead flirt, ends up dishing out insults to the other teams, and Shizuma takes his quietly without confrontation, leading to the aggressors leaving. Hounan successfully defeats Tsubakimichi in their Group Tour match and moves up the bracket. A few days before their race against Saisei, the two teams are featured on a television broadcast. Shizuma pulls Nana aside to talk to her again.
"... Sakurai-san."When the two of them return to the announcer room, Shizuma adjusts smoothly to his role as coordinator for his team, still dispensing advice for Nana at appropriate intervals. The show ends with both teams tying in the games.
"You were in communication with Reiji-sama recently, yes? I was aware of it from his side."
"Um, that's... because I was unwell during those days... and he was worried about me."
"Yes. I know about that. However, I need to ask of you what I asked before. If you keep this up, it will become very dangerous.
Reiji-sama is the sole heir of the Suwa family. He has been living up to many heavy expectations since young. Now, he holds important positions in both Galaxy Standard and the Saisei Stride team. For someone in the spotlight like him, it is easy to hurt them. If your communications become public, it will spread like wildfire. Everything he has worked for will all be gone. He understands this risk, and he is willing to take it. But what about you?
I will be honest with you, Sakurai-san. Once he sets his mind on something, I cannot stop him. He is prepared to bear any and all responsibility that comes with his choices. Because of this, I need to ask you. Are you willing to bear the same risks as he does?"
"... well, I will ask it in a more simple way. What do you think of him?"
"I will end our conversation here. I await your answer after EOS is over. My apologies for taking up your time. Till then."
The match between Saisei and Hounan takes place at an amusement park called Smileland. During the race, we get to hear the telepathic conversation between Reiji and Shizuma through Nana's ability. The two of them reminicise about their past for a few moments before Reiji's burning determination drowns out the conversation. However, Hounan wins by a fraction of a second, thus ending Saisei as third place overall in the rankings. That night, Reiji waits outside the hotel at the park for Nana. After the two of them talk and Nana leaves, Shizuma arrives on the scene, having searched for Reiji all over.
"..."The next day, both the Hounan and Saisei team receive tickets to the amusement park from Hounan's sponsors. Nana's best friend Riko hatches a plan to get her and Reiji together, and as a result the four of them (since Shizuma tags along) end up exploring the park as a group. Contrary to the other three's high spirits, the thriller rides are a bit too much for Shizuma's nerves and he ends up getting tired out very quickly. The day ends without much mishap, however.
"What are you intending to do, sitting around here like this?"
"Even if you are not going to come back yet, at least give me a reply. I have been looking all around."
" [sigh] I already know what you're going to say. I'll hit you when you say it."
"... ahahah. Hitting an idol's face... you're being a bit cruel."
"Even if you're an idol, you're Reiji first and foremost. Especially tonight."
"... I'm sorry."
"And what do you mean by this?"
"I've gotten you all tangled up in this. Even with you here, I couldn't do it.
My family trade, Stride, Galaxy Standard... I thought I could do all of it. Not just be able to do it, but aim for the top. That's what you told me too.
This is our last EOS. I wanted to win it by any means. That was what I committed myself to.
But I couldn't succeed in the end.
Maybe... if I only focused myself on running, we could have won."
"................ I knew you would say that."
"Present your face."
That hurt! Are you for real?!"
"Of course I'm for real. I'm as serious as you are!
Your family trade, Stride, Galaxy Standard, all of it. Of course you could do it. Especially since you're so serious about it!
There were so many people supporting you along the way. And you're just going to put all the blame on yourself - the moment you think this, everyone's hopes tied to you will all be gone. If you're going to think that way.... aren't you an idiot?
You're rejecting me, and your past self's work."
In the end, it was you getting angry that had the fastest effect. I understand now.
I sure am a greedy person, aren't I? Japanese dance, our group, and Stride. So many things."
"Don't say that."
"I can't just choose one. That's something only an idiot would think. I want to do everything."
".... [sigh]. Weren't you thinking about something else just now?"
"That wasn't what you were thinking of? Whoops."
"... well... we will save this topic for another time."
"Wow. The in-law sure is harsh."
As with before, time passes. The Saisei team show up for Hounan's final match against Kakyoin as spectators. Nana's telepathy activates Overflow, a phenomenon where all the attendees are connected in a network of thoughts. The effect spurs the Hounan runners on, and they claim their victory as overall grand champions. In the aftermath, the Saisei team meet up with them and give them their tearful congratulations. Shizuma is once again the most calm of the group. Having his doubts about Nana extinguished after her performance, he acknowledges her as someone important to Reiji and tells her to go on ahead and meet him.
In the epilogue, Shizuma once again helps Nana to coordinate training for both their school's teams. When the boys end up having an abs contest, he reminds them to keep decent while Reiji covers Nana's eyes. He tells Nana to personally time for Reiji with a knowing look and later on leaves the two of them to do their own thing.
Shizuma can be honestly summarized as the caretaker archetype. He is usually soft spoken and very polite, though a little fragile (mostly physically, though he doesn't take sudden shocks easily either). He cares a lot about his best friend, possibly to mother hen levels. Even if he doesn't really have strong ambitions like Reiji does, he is a very devoted partner and finds it fulfiling to just support the other in his own ways.
I really hope we get to see more of his backstory. He is a well-written character and it'd be a waste to just leave him in the dust.