When Tsubomi was a high school girl, she had a forbidden relationship with a female teacher. Now she works as a teacher and spends time with her beloved student Mamiru. Mamiru tells her, "I love your smile, teacher." Tsubomi is unable to smile back at her, and her past forbidden love keeps her from going out of Tsubomi... However, Mamiru's single-minded feelings gradually take over Tsubomi Kokoro and body.