Not Horror: Nana Fushigi Tanteidan

Freshly moved to Daimon-machi, Tom Satou meets a mysterious young man named Kibayashi.

Lately Tom has been troubled by something, and asks Kibayashi for advice.
It's about this new "Seven Wonders School"...
Tom has noticed a lot of phenomena that can only be thought of as supernatural.
Upon hearing this, Kibayashi agrees to help Tom solve the mystery.
Thus, the young friends begin their adventure.

[From DLsite English]