The bully or not?

The next day Alex was a bit stiff. He was more attentive to his surroundings than usual. He, as I mentioned, was extremely curious and he was thinking 'Actually, detectives need to pay attention to everything to discover the truth, even to things that seems to do not have anything to do with the case, ah, like that girl who has no relationships, or that boy who chats too much'. Now, if you are wondering why he doesn't know their names, it's because he only remembers his friends' names. Oh, and the two people mentioned are normal high schoolers. And, about his observation abilities, they are on pair to zero. Infact, he can study only in certain circumstances adopted by his parents (cruel people). There was another person extremely attentive. Daisuke. Who, differently from Alex, didn't have any attention issues. Luckily. He obviously understood that something was going on regarding his two friends and didn't want to be left out. Because of his absence the day before, he didn't know what happened with Kei's phone, but he could feel the air was a bit tense (just so you know, he doesn't have superpowers, it's just a way of saying it). He was still doing his research about Kei's mother, although thinking to have done some mistakes because from his research it seemed she was a famous musician who had four children, all of them famous. And Kei obviously was not between them. At some point of the morning, the math teacher asked Kei to go to another class and ask for a ruler. He had to go to a second year's class. After a little, in that class, a muscular boy with blonde hair saw, in the hall, that somebody was arriving. Somebody he knew way too well. 'Ohh, it's him, that stupid, weird childhood friend of mine. Great. This too difficult lesson will finally stop. Should I greet him? Or not? What if he hates me because of that person? Nah, we are surely friends, like everybody'. Now, are you thinking he has a childish mentality? I think I kind of agree. Anyway, then Kei entered the class. He saw a boy (that same blonde haired boy) who was smirking and who was moving his hand like to say him hello without being noticed, and Kei interpreted it as a mocking gesture, ignoring it. Infact, he was thinking that that boy wasn't worth attention anymore. He was thinking that that boy was simply a bully. He always questioned how that boy had the reputation of a friendly person. Infact, that boy was his older brother, Kenji. Even though their names are similar, they are quite different. While Kei had always been a quiet kid who talked almost only when asked directly (one of the few, if not the only exception, was when he talked for the first time with a girl, when they were children, who became his best friend 'till the age of nine, when they stopped seeing each other), Kenji was the tipe of person who started the conversation. While Kei gave much importance to rationality (although he is totally average in math for his family's standards), and kept thinking with his own mind (things regarding his sister are a strange exception), Kenji only listened to his instinct, but, when anybody asked him his opinion about something, he would say something he heard from adults or people close to him, or he wouldn't talk at all if it's the first time hearing about the topic. A thing that they had in common was that they both wanted friends, although Kenji was open about it, while Kei was more of an insecure person, who, if directly asked, might even blush, answering something else to change the topic (he doesn't blush if not asked directly). Their relationship was probably partly a misunderstanding, even though it is undeniable that Kenji bullied Kei.