
That part didn't. That part looked like battery. At that point, there was no consent.
But then he was thinking about how good if felt and if he should. Then he opened his mouth and said, "okay."
Now, there is consent and what happens after is consensual (until he says no, if he says no).
The part that happened before he said okay was without consent, and that was battery, possibly sexual assault, but there was no penetration.
The part that happened after he said okay was consensual, and that's when penetration happened.
I call rape by name even when I like it in stories (and I do like some romanticized rape stories). But if one person gives consent without being under some kind of threat, it's not rape. This isn't a romanticized story of seduction because clearly we know it all goes horribly wrong...but he did consent in this chapter before penetration. So far we have manipulation and battery, but we also have consent for sex.
rape is still rape
And I still love yaoi