Indeed; if you ask him, he clarifies that his love for you is of a romantic nature. Also, you can have a purely platonic friendship with him, which plays out slightly differently. So yes, it is different from what he feels for Aleusha.
That being said, I'm not sure whether he really is asexual. With Saorise it's pretty clear that she is asexual as well as aromantic. Markus is clearly not aromantic, but I also think that him being asexual isn't quite as clear cut aqs it seems. First of all, he clearly mentions masturbation and he also explains that he runs a sex shop because he is fascinated by sexuality. He also has a noticeable amount of sexual experience, though he doesn't comment on how much he enjoyed it or not. Also, he is the one who brings up the possibility of sex and he gets annoyed if you answer his question by asking him whether he wants it. (Notice that he doesn't answer in the negative, he just insists that he is asking YOU.) Should you sleep with him, he will say that you feel exactly like he imagined it, which means he has been preoccupied with such thoughts. Should you decline, he will voice relief, but can also admit that he isn't exactly happy with how things are with him, merely content, and that he doesn't consider changing his mind an impossibility. All things considered it seems he is conflicted/inhibited about sex, rather than simply disinterested in it.
Coupled with his other statements (was more in love with his image of others then with the persons themselves, feels love most acutely when he watches you from a distance, also his fear that he can't live up to your picture of him and his interactions with Dream-Aleusha) make me wonder whether this is a part of a greater issue. It's like he is uncomfortable with the idea of getting too close to someone, and that might also show on a physical level. Sorry for my rambling, but I think Markus is a really fascinating character, so I love to dissect him.