Blue always says "Smell ya later" to the player character, even if you're playing as Leaf, the girl. That can only mean one of 3 things thing:
1. Leaf smells.
2. Blue is a male tsundere that likes Leaf but only knows how to tell her through petty rivalry and insults.
3. Both. Leaf smells AND Blue likes her and can't express it.

I like to think it's option 3.