I'm... hoping/assuming that Osanai is making funny faces to joke around rather than anything else. Because otherwise... wat?
It's quite probable she's trying to make him laugh, so Hime gets even madder at him. Edit: No, I'm pretty sure he already laughed hard an loud, actually.
I'm really liking Osanai, if this was a VN her route would be my first choice.
Bfoh!?
Snrk! ...Snrk!*Cough!* T-That's not...!
You've got it all wrong, Himekawa-san!
I wasn't laughing at you
There's a severed head behind... Dammit, Senpaaai...That grin is totally disgusting!The hell!?
What're you laughing about!?
You are seriously unbelievable!Mbleh~...