Saiki despised relationships, platonic or not. It attracted too much unnecessary attention which was the opposite of what he wanted. But that all changed when he met you.

He hadn't planned on getting close to you, or anyone for that matter. Somehow, you eventually grew on him and he became obsessed, even if he denied it. But despite being a powerful being, Saiki hated confrontations and especially confessions. Maybe he would just admire you from afar, or perhaps make you fall for him and confess first.