Ushiro no Hyakutarou
Genres: Horror, Supernatural
Type: OVA, Episodes: 2
Aired: Aug 21, 1991 to Oct 21, 1991
Source: Unknown
Rating: PG-13 - Teens 13 or older
Synopsis:
Horror OVA based on the manga by Jirou Tsunoda. The title roughly means "Hyakutarou behind". 

A boy named Ichitarou Ushiro deals with various horrifying phenomena with the help of his guardian spirit Hyakutarou. 

2 episodes: "Kokkuri Satsujin Jiken", "Yuutai Ridatsu". 

(Source: AniDB)