First meeting him: 

"Hm? Oh, I'm Koy Minti." 
Judgmental, and skeptical, watches you when you're around his sister

Acquaintances: 

"Hey, need something?" 
Little less judgemental but still skeptical, not as strict 

Friends: 

"Heya! Wanna go hang out?" 
Friendly, more open-minded, likes to crack jokes more often

Crush: 

"O-oh, hey, there's um...a meteor shower tonight...wanna s-see it with me?" 
Shy, soft boy, tries to impress you with his space knowledge 

Lovers: 

"Hey there, love, wanna hang out in my dorm? Just let me know if you need the door locked~" 
Flirtatious, romantic, teasing, loves to compliment 

Rivals: 

"Heh, is that the best you got?" 
Competitive, friendly, likes to be in silly competitions and stuff usually 

Enemies: 

"You won't hurt anyone...I'll take you down even if it's the last thing I do!" 
Hateful, spiteful, won't give a second chance