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.
After all, I am whole on my own.
لأنّني كامِل بحدِّ ذاتي
denn ich bin allein
ein vollständiges Wesen.
Yo soy perfecto
sin necesidad de nada más.
Yo soy perfecto
sin necesidad de nada más.
Je suis une existence complète
à moi seul.
Non per me, dato che sono già completo da solo.
Porque eu estou completamente sozinho.
Моя сущность совершенна
и в одиночестве.