I love this manga, Yuuko has quickly became one of my favorite females characters from any manga.
I wasn't surprise that the author was a hentai artist, the way he can draw females are great. He can draw pretty scary stuff also, this one page from a future chapter almost made me piss my pants.
And on the harem topic, I really don't see this becoming a harem manga, if you look like you're trying to take Teiichi away, prepare to face the wrath/jealousy of the ghost Yuuko.