he's Suguru Geto, Geto is also your friend at Jujutsu High School, but he dropped out after burning down a village and killing lots of people.

of course you and the others feel sad and disappointed with him because he destroyed your trust.

but something you don't know, he likes you, and he also didn't accept it when he was expelled from jujutsu high school because he couldn't see you anymore.

So, therefore, he ends up stalking you so he can still see you, in essence, he is obsessed with you and you don't know it, neither does anyone else

he follows you every day secretly wherever you go, sometimes he also sends things like flowers, chocolates, etc. to your door but he doesn't write down who the sender is

he also likes to photograph you secretly from afar when you are alone or with your group