to be fair , it is a one shot so it had to be rushed (i noticed it to tho shdhdjdj)
I guess since I'm maybe like Sakai I understand him. He loves Katou before he knew Katou likes him. You can see it the way he becomes confused when Katou don't want to walk home with him but not angry. He reaches out to Katou and whatever actions Katou takes is endearing to him. He slowly becomes obsessed with Katou's expressions. It's a subtle and slow way of loving someone. When you find yourself looking at the little things. It's not blushing hard and your heart doesn't always beat fast but it gives a feeling like you're floating. It's very interesting the different ways people fall in love.
Hmm I understand how Katou fell for Sakai. Sakai's a transferee and suddenly became friends with Katou who seemed to be isolated most of the time. Thus, this friendship is something new for Katou, hence he was easily infatuated with Sakai. But Sakai's feelings for Katou is doubtful for me. I mean IMO he only liked Katou because he reacted to him differently and he had known and noticed that Katou had liked him for a while now. It's like he's liking Katou since Katou likes him. I cannot sense love between the two.
(〜￣△￣)〜