The Secret Stairs

[From Kotonoha]: One rainy day, the young woman Natsuki encounters a high school student in the street. Acting on an impulse, she gives the girl her umbrella and walks away. It turns out later that the girl, Michiko, is the younger sister of Natsuki’s

Wizards are never a single entity. That is, they are composed of a partnership of the "holder" and "caretaker" of the stone. Celeste is the "holder" of the stone, and she's in a hurry to become an independent wizard. But her partner, Chris, is not the easiest person to work with... 

"In the Afternoon..." is the sequel to Konno Kita's earlier work "Nowhere to Go". Moriya's antics continue, and Miwa comes down with a cold. (from Lililicious)

[From Lililicious]: Nowhere to Go is another girls' boarding school story, but the deviousness of one of the main characters is what makes it memorable. It has a sequel called In the Afternoon....

From Bliss: Haruka and Saya spend their days living peacefully with their father in a small town. However, when a new neighbor moves in, unusual events suddenly start taking place. Strangely enough, they all seem to be related to Haruka and Saya's mother

[From Lililicious]: Under the Rose is a love story between two sisters who meet years after their birth.

The Secret Stairs is a supernatural story set at a girls' boarding school. It focuses on friendship between girls.