Yandere Lily Holic -Sacchan no Aijou Hyougen-

A yandere yuri adventure game featuring girls with twisted desires
Mikagami Sachi, an honor student, has a certain secret.
She's in a romantic relationship with her classmate and friend since junior high, Kisaragi Hotaru.
However, it's not just any relationship;
they have a distorted bond where Sachi expresses her "love expressions" in twisted ways towards Hotaru.
While portraying herself as an honor student, Sachi continues to vent her dark desires on Hotaru in secret.
But one day, her school life starts to fall apart.

[From itch.io]

Title changed from さっちゃんの愛情表現 in November 2023.