Urotsukidoji IV AP

[godleydemon]

SO before anyone shouts "this is old" I know its old, but I suddenly ran into something that I found quite confounding. There is a nice AP in this video but for the life of me I can't find a subtitled version of the anime/hentai. I've searched everywhere I can think of and the entire reasoning for this is because I want to know the reason for the AP. It didn't exactly make much sense to me and the youtube translate for subtitles is absolutely horrid.

Now then, any help from anyone explaining this one is much appreciated.