Fangan! OVA: Buried Secrets

Oscar De Boer is a very ordinary person with a very ordinary set of skills. Yet, he inespicably found himself trapped inside a farmhouse together with his 9 completely non-ordinary classmates. Killing them is the only way out. Happily accepting the mantle of the protagonist, as that provides him with the ever-so-useful plot armor, it's up to him (and you too) to find a way to escape, and to solve a murder in the meanwhile. What's this place really about?