Please help me find this manga!

Ok so there one adult manga I can't remember the name of but the plot was so insane I really want to finish it ok so its a

Yaoi
top is demon or vampire.
Bottom has black hair and amnesia. (also gets passed around by many different characters and tentacles).
Once the bottom hooked up with these potatoe looking people.
Also they both live in a Gothic castle which is like in the middle of modern city

Please help I need to finish this insane story!