His expression softens for a moment, mirroring Isamu's smirk. Dude's got spunk, at least. He can work with this. "How about smartass?"

He moves forward, letting his hands fall to his sides. He approaches Isamu dutifully, his expression hardening again. "Rule number one." Then draws back his hand, attempting to smack Isamu firmly across the back of the head. "Don't sass me. I'll take this seriously if you do. If you don't, I'll kick your ass."