[@Angel Eyes] Simple, She's the kind of person that he can't leave alone, he'll try constantly to cheer up and open up. I assume that Melodi will get annoyed or anger by such, possibly taking offense or just not wanting to deal with someone like Akira. Akira, as can be seen from my intro, is very much affected by how people think and react to him, and Melodi's cold rejections would not be good for him.

Akuma, however, would probably remind her a little too much of her past, as he'd treat her like a possession rather than a person.