WHY?

because he is hansom
no just kidding. I actually do have reasons that are a little more complex.

his whole character relies on his kindness. he becomes a sorcerer because of that kindness, decides to use it for people he thinks are "weaker" than him. but he doesnt' realize that he isn't as strong as he thinks he is, and that no one is protecting people like him.

his friends are sent to die and the only thing he can do is watch them. all for "saving the weak"... he's strong and satoru's strong but even then he's not immune to pain. he is not immune to suffering. he forgets that. and that what made him become a curse user.

upon becoming a curse user, he instead uses his powers for those weaker than him... but for other sorcerers. and in terms of the story, while it seems like a huge shift, it isn't really. he still is operating under the assumption that he's strong and everyone else is weak and he has to protect them. which is. so great.

he's kind to a fault and that really reflects back on how he sees the world as is. Suguru's undoing was his own kindness...
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