Okaya prolly fell Inlove with nagare after he said the shit "I'll never run away from you" cuz okaya is a scary dumbass fuck so hearing that from someone's mouth prolly made him twinkle inside a bit, he couldn't recognise the feeling he was feeling was love so he prolly thought he just liked toturing nagare. Honestly I have seen so much of that kind of trope in BL it's insane