I'm still of the opinion that the moment she reveals she's Fumi tan and confesses to Kotaro it will be the moment he realizes the bullies are the ones he truly loves.
Anyway, it's hard to say who is weirder, him for complimenting a girl like that or Sumika for blushing so hard for such a compliment.
I'm still rooting for an harem ending, and if that's the case, I'd love to see Sumika included.