Entirely average series. It was interesting seeing a seinen love triangle with two males instead of females but the end was handled bad. Having them all be friends again, I really cannot see that, at one point the two would split up and this was what should have done it. That would have made the story better too, a bold leap by the author instead of the weak ending here.
I also have no idea why the girl could detach her head. There were no other supernaturals in the story. Noone commented on her ability. While used as a physical prop I see no development in character from that. Really it just distracted from the otherwise generic plot.
5/10.