Mukai Shirou

Mukai Shirou (向井 司郎, Shiro Mukai) also referred to as "Shiro" (シロ) is a first year student at Kushima High School.

First Years Uprising
Shirou is introduced stood on the school rooftop along side Shake viewing the fight occuring on the school ground.

As Shake begins walk towards the staircase when challenged to a fight by Shiiba Gaku. Shirou asks him should he and his other companions go in his place.

Looking down over Marumo Taiji after Shake mentioned that he might be worth his time. When someone says what a Sake-esque to say. Noticing Shrio's blank expression he's asked if he's jealous. Shortly afterwards, inside the school while walking down a staircase he's attacked from behind.

After being kicked in the head, Shirou grabs the student's leg and questions what he wants. Avoiding being kicked Shirou slams him into the wall. When Tanaka Hiraori mentions he's strong, he and his allies will take him down. As Shirou mentions his words are polluted, he declares to crush anyone Shake doesn't acknowledge. After crushing the face of another student. Walking towards Hiraori he mentions to get the top he'll have to do it stair by stair. Shirou is then surprised to see Taiji appear behind Hiraori and crush the crowbar he was hiding.

Telling Marumo Taiji not to interfere as he was looking for to crushing him for disrespecting Shake's words. Watching Taji pick up the defeated students. Questioning if they're the type of guys he hates, Shiro mentions that's why he crushed them. When the area becomes covered in smoke, Shiro turns around to intercept Hiraori's attack until seeing bodies being thrown at Hiraori. Telling Taiji not to interfere he questions if he's aiming for the head of Windmill. Upon seeing Shiiba Gaku recover and calls out Shake. Shiro introduces himself and mentions Shake is somewhere far above him.

The next day while entering the school yard he tells Gaku and Taiji they're in his way. Walking past them he begins to head inside.

Inside the school gymnasium Shirou is seen working out in the rafters until he's suddenly questioned how he got up there and if he's a monkey.

Being mocked by Gaku, Shirou climbs down from the gymnasium ceiling and asks if he came to taunt him. AGaku swings his fist towards him until Shirou grabs it and says they have something in common. Revealing he despises Shake, Shirou lowers him to his knees and punches him. Telling Gaku he can't win against him because they're simular and that he's not tough enough. Mentioning he also hates being looked down upon, he reveals his loss against Shake and because of that he can't stand his face and wants nothing more than seeing Shake beat down. Angered, he says there's meaning to taking Shake's position as head and repeatedly punches Gaku. Explaining the reason for his training, Shirou delivers a final punch and starts to walk away. When Gaku mocks his explanation Shirou starts to become annoyed.

Gaku gets back to his feet and swings for Shirou but he avoids and strikes him back down telling him to be a good boy and stay down this time. As Gaku tells him that hurt he gets up and hits him with a round house kick and laughs after doing so. Unassumed Shirou informs him the only one getting a beating is him and knocks him down. Getting up Gaku begins panting and says he's different from him as he doesnt have the will to imrpove himself, in someone ele's shadow and no matter how many times he gets beaten down, all hes gotta do is get up everytime. Shirou says he understands what makes him tick, however, what value can be found, in winning without winning the title of head without any effort. Shirou and Gaku then both punch each other in face simultaneously.

Continuing to fight their brawl spills to the front entrance where they knocked down who was Marumo stood outside. As Gaku questions what he's been up to, Shiro says he's in his way. When Taiji reveals his experience of formerly being a gang leader until being beaten by single man. Taiji then asks Urabe to come at him with everything he's got and he'll return it with everything he's got. Both Gaku and Shirou watch on.

When Marimo picks up Urabe, Gaku questions what he's doing, Marimo says he's taking him to the infirmary. Asking Gaku and Shirou if they finished their fight, if not keep going and he'll carry whoever loses. Shiruo tells Gaku the fight has been ruined thanks to him. Gaku tells Shiro not to try and run away with a pathetic excuse. Marimo sugguests they settle it in a different way, carry the remaining members of Hydra to the infirmary, and whoever carries the most wins. When Gaku complains about it, Shirou accepts and Gaku says that's low. As Gaku begins carrying two people Shirou taunts him saying its his win as he's carrying three. Witnessing Marimo carrying multiple people he calls him a monster. The three of them go back for the remaining members and return to the school when Gaku complains there's too many of them, and questions how many trips has it been. Shirou tells him he bitches too much while Marimo asks them both to shut up and carry.