He's not being a real tsundere... he's just bad with words... it's mostly her own misunderstanding..My guy better have the biggest of apologies and atonement actions ready if he wants to pull of this tsundere act.
Of course he'd be immature... he's a kid being nervous around his crush...Hope she doesn't get with that boy hes to immature
Blasted jackass, Miruporon deserved better than this.
Then again, Emmerich was kinda annoying at first as well... Hopefully the author can make the redemption acceptable.