Shijin-sou no Satsujin Series

A dozen students decide to rent a boarding house in the mountains. A nearby bioterrorism event results in the house being surrounded by zombies. Initially they are repelled by the occupants using swords and spears, but then a murder occurs inside a room locked on the inside. A human could not have made the bite marks that killed the victim, but a zombie could not have got into the room to make them.

More murders occur. Theories abound, but are knocked down as soon as they are proposed. The solution is an extraordinary exercise in deduction.