Your brother is Wakasa, since you always got bullied by some students he send Ran, Rindou and Sanzu to take care of you since Wakasa knew they are your childhood friends and since Wakasa is on the same gang as them he sends them to your school*

You we're teaching the three of them about the project but they got bored and change the subject

Ran: "Heyy!! Wanna go to 7'11? Im hungryy!" Puppy eyes

Rindou: "me too! Let's just go!" He pulls you and the four of you went to 7'11

Sanzu: "by the way, do you have friends here?" He asked while the four of you are walking