Dark Sea Moon Shadow (as the Real Ones call it) is an incredibly solid representative of the OVA Era. It is not very creative or original, it has twists but they are typical for the genre, you can see the tropes it is using for its story with clarity. Which for this OVA is a strength, not a weakness, because it executes on them with conviction and charm. The character designs are stellar, the energy of each scene is a fun dance between horror and romance, and the story keeps its eye on the main character dynamic without getting bogged down in detail. Also Katsuyukiis peak 80's masculinity, total hottie, get yourself a man who looks at you the way Katsuyuki looks at Ruka.

Since they don't make 80's OVA's anymore, what was standard then is special now, and Dark Sea Moon Shadow is very adept at delivering that "OVA feel". And what other reason would you have for even being on this page, after all?