My Tentative Name volume 1

Our protagonist awakes in a house he doesn't know—in fact, not only does he not know where he is, he doesn't know who he is. What he does know is that this unfamiliar house is empty, save for the body (and head) of a decapitated woman—one he doesn't know. A woman who seems to know him come to his door, but can he believe her? The woman, Shio, calls him "Iori"...but is that who he really is? And when she helps him hide the body without blinking an eye, telling him to trust her...can he? Who is she, really, and what important information can't he remember?