Three years ago, Serizawa was troubled with about his psychic powers. One day, he was visited by the boss, Suzuki Toichiro. Serizawa ends up trusting him since he's the first person to understand what he's going through. But Mob then brings up the fact that Serizawa is being used and tells him, "I'll be your friend." Hearing Mob say that, Serizawa... 

Meanwhile, after defeating Sho, the boss starts gathering up the energy he was sharing with his followers and turns into an energy monster.
Because my younger brother 
was afraid of me, too.
لأنّ أخي الأصغر كان خائفاً منّي أيضاً
Weil mein Bruder auch
Angst vor mir hatte.
Yo también asustaba a Ritsu.
Yo también asustaba a Ritsu.
Parce que j’effrayais
mon petit frère.
Lo so perché anche mio fratello aveva paura di me.
Porque meu irmão também tinha medo de mim.
Меня тоже боялся младший брат.