[ oooh OOOOH she straightens, thinking she's starting to understand. ]

K-kun can be saying we're closer friends than, um... K-san. I'm sorry, I'm not sure how to explain. [ she brings her hands up to her chest, thinking pretty hard. ] When I meet most people for the first time, I'd say, Hello! It's nice to meet you, Person-san. But if it's a friend or a classmate or someone like that, I may say, it's nice to meet you, Person-kun. Though since you're my senior here, calling you K-san makes sense, too...