Even if he ended up going with the whole thing. Doing that to someone who is sleeping, while they havent agreed or talked about it prior to the events, is still not ok and usually classifies as SA
Agreed
Amen
Except that the literal person he's doing it to is consenting to the act going on, doesn't perceive the event as assault. The mangaka has shown over and again that Garam is just as kinky/carefree with how they go about their sexual relationship, he just doesn't want to be inconvenienced by it. Not saying SA of this sort doesn't happen in RL/isn't valid, but it's definitely not the opinion of either character in the scene.
The comment section: how can he do this? It's nonconsensual! How horrible! This is SA! Seme is piece of...
Uke: IF YOU DON'T PUT YOUR DICK IN ME, RIGHT NOW!