Tried to submit this:
They are the same person. Almost all their art has both names tagged. Vice versa would also work I guess.
Miroukitsu is their Twitter => https://twitter.com/miroukitsu/
Mitsuharu is their Pixiv => https://www.pixiv.net/member.php?id=871037
I get an error saying "miroukitsu is already aliased to something," which is not true, since the tag shows as is on all the artist's posts.
https://e621.net/artist/show/25198 says that miroukitsu is aliased to "mistuharu [sic]", but it does not show up on the wiki page https://e621.net/wiki/show/miroukitsu. It's a typo anyways. Should be mitsuharu not mistuharu.
Updated