Dude was trying his hardest not to see his childhood friends as something else, then they started to give him strong signs that he might not be able to keep on seeing them as just childhood friends. He was confused, keep things as always or clear his feelings, he was recommended the latter and took a step forward into seeing one of the girls (Shio) as something more. But the moment he tried to confess he got rejected, Shio choose to keep things as always and now he doesn't believe to have the right to see his friends as something more than that. Dude got traumatized and decided to numb himself of having any romantic feelings towards his childhood friends, after all that's what they have always been and will always be and what happened just proves it.