Yui Suzuhara is secretly going out with her homeroom teacher (the protagonist).
One day, she is summoned by the PE teacher Tougo, and shown some incriminating photos of her and the teacher on an early-morning date.
If their relationship is found out, they'll never be able to be together again.
"I-I'll do anything you want, so..."
Young Yui didn't yet realize the full extent of the word "anything", but the promise was made.
Tougo immediately makes sexual demands of her, and Yui is forced to surrender her body to him for the sake of her beloved.
The protagonist starts to realize something is off with Yui of late, and becomes suspicious...