i like to think that tendou smiles and laughs a lot during sex/masturbation because he's happy and excited, and god he feels good. i have no doubts that he's a switch & bottom pref--you get to see his smiles and laughs fade into gasps and cries whenever he's submissive, and when you break him he goes quiet. somehow, it's more satisfying to pull him towards the edge, shutting him up and making him completely speechless than it is to rip out every moan and growl you can from him ԅ(¯﹃¯ԅ)
YES oh my god he's so happy and smiley during sex and mastubation, cracking jokes and telling you how much he loves you. even if he's alone.
but omg I've never thought about sub tendou... interesting... i feel like he's a bit of a brat, only enough to tease you a little before letting himself go completely. very sensitive to your touch, whining almost immediately when your hands brush over his chest and wrap around his throbbing cock <3