Izuru loves his brother to death, but will call him out on his bullshit in the most cold hearted way possible. For example:

Izuru: *playing video games* So how are you and Nagito?

Hajime: *also playing video games* Me and Nagito haven't really hung out this week. I should call him sometime.

Izuru: Oh you've hung out this week. You've hung out last night judging by the moans I heard from you room.

Hajime: *blushing profusely* I-I, pfffft, WHAT? W-WHAT ARE YOU T-TALKING A-ABOUT????

Izuru: Don't play dumb with me Hajime. These bags under my eyes aren't gained from staying up late to finish home work. No, I've gained these bags under my eyes because SOMEONE is a loud bottom.

Hajime: ...

Izuru: I don't mind that you're dating Nagito. In fact, I support your relationship with him. The only problem I have is that you're loud. Quiet down please. I don't like hearing my brother moan in lust. It's creepy.

Hajime: Okay...

Izuru: Also I just won the game.

Hajime: DAMNIT IZURU!!!!