Responses
Well, I think he's pretty harsh with people he doesn't care about, even if he sleeps with them. I'll assume they're all partners who are also indifferent to him. He also tended not to realise/care how things that seemed fine to him might be upsetting to Kyouhei, before he got to know him better (I love how Kyouhei was actually pretty blunt about what he found unacceptable, which feels rare). But he hasn't ever gone out of his way to play with Kyouhei's feelings or anything like that, and I agree that his teasing phase was more affectionate than nasty. (And, of course, he's looked out for him a lot, too.)
The seme is not much of an asshole compared to some other yaois I read regardless of the "almost rape trope of another character making the seme look good" like what others say and I don't see him as a manipulative character either. He is rather the like-to-tease-someone-he-likes kind of guy but gentle. Just my opinion.