Tsukasa considered himself the hero of his story, the one who'd defeat all the bad guys. But in the end he didn't notice he was becoming the villain himself, filled with his own ego.

He destroyed 'evil' things in his path and 'defeated villains.' Yet he was clearly just an average human being who went too far because he wanted attention, not even realising his downfall into his new self.

Someone had to do something. That's your cue.

"I'm the main character here! You should all like me!"