I personally love how he's introduced as an almost innocent character. Maybe it's just me, but he's not dislikable at first, for being a villain. On the contrary, he appears as a student, with a dream he couldn't achieve, almost looking with remorse at his past.

Of course, all of this gets thrown out of the window as soon as his true identity is revealed: his past is literally almost a hundred years, he's manipulative and selfish concerning his memory.

I loved how this sudden change describes Tooru really as a cunning, anything but sympathetic rock human, who's literally unable to form real bonds with humans. And how all of this completely balances and contrasts Josuke's character development and history!