Gakuen Benriya Series: AntiqueHeart

Saito High is a high school with its spiritual beings and a principal whose hobby is collecting occult paraphernalia. The school has the prophecy-chosen members of the Holy Student Council to protect it. These students have problems of their own; Haruto Houjo, the president, has a way of summoning spirits, and would resign from his duty for a normal life if it weren't for the principal. Kazumi Ryodo, the next member, is good at being possessed and has something for the Hanako. The last member is Mutsuki Asahina, who is a master of exorcism and is attracted to small boys. Unfortunately, these three are in charge of keeping the school in line and defending the world from supernatural beings, and this mission brings them through wacky predicaments.

60 years ago, a young woman was left to die in the abandoned school building behind the exclusive Seikyou Academy. No one knows why. No one knows how. But the horrifying tale and the legends of the ghostly haunting that followed live on to this day. Perhaps it's not so surprising then, that among Seikyou's many school clubs is one for students interested in "paranormal investigations." What might raise more than a few hairs, however, is that the founder of the club is the ghost herself. Unable to remember how she died and trapped in the grey land between life and death, Yuuko latches onto Teiichi Niiya, a freshman who can inexplicably see her, and together they and the other unsuspecting members of the club begin to unravel the many dark mysteries that surround Seikyou. Will unlocking the secret of Yuuko's gruesome death finally free her? Or will her sudden close association with a mortal have even stranger repercussions on both of their existences?

Shinokita Reiko and Yajima Junko are second-year high school students who travel from school to school fighting bad guys, ninjas, yakuza and corruption. At this high school they encounter a secret ninja order and a corrupt administrator, as well as a tragic death in the distant past. With the help of Kotetsu, a skilled ninja, they set the school to rights, but not before leaving several broken hearts behind.

Originally an April's Fool in 2007, this one episode OVA is a spin-off of the School Days game by 0verflow, and shows Kokoro Katsura, the little sister of one of the main characters, from her other side. A mahou shoujo out to save the world, or something like that.