That reward is sweet indeed, and the way his face eases into pleasure expresses that plainly. The throb in his groin is overwhelming, and if not for his restraints he'd be able to grind up against Byleth better.

"Adorable? Please, I would not name me such. I am...well aware I can laugh. I simply have elected not to." Not yet, he can't give in too easily, that would ruin the chase, he thinks. He's certain Byleth wants to bring him to his knees on his own, so to speak, not be handed an easy victory.

He does watch the telegraph of that feather, however, and his eyes grow wide as it begins to go closer to his arms then touches them. Immediately he jerks against the aetheric bindings, and they glow brightly as they strain to hold him back.

If he was after where he's sensitive, this would be it, and while the wet friction of Byleth against his dick is heavenly, it isn't enough to stop him from what happens next. As Byleth goes from feather to fingers, Emet-Selch lets out a strained sound that's almost like choked laughter, squirming and jerking from side to side, pulling at his bindings with alarming strength.

But then as the sensation (not to mention that last comment Byleth made) becomes far too much, and he can't seem to keep his senses about him. Thus he ends up accidentally engaging his glyph, and while he doesn't break the aetheric rope...he bends the bar holding him with a horrific metal sound.

Oops.

Assuming both the gylph and the metal bending gives Byleth pause, he likewise stops in that moment, surprised at himself. Peering up at the bar, he blinks at it, looks to Byleth, then snaps his fingers—fixing the bar and reinforce it.

"...Mine apologies. I think it is safe to assume that is a ten."