Kusari no Kankei ~Tsubasa o Mogareta Kago no Tori~

Tatsuya Shiihara had someone he liked.
Her name was Kugumiya Akari, a cute girl with a bright personality.
He wanted to be more than just friends.
With determination, Tatsuya confessed, and they became a couple.
Their life together was going smoothly, and Tatsuya enjoyed every moment spent with Akari.
But one day, he caught sight of his best friend and Akari together.
Thinking it must be a mistake, Tatsuya tried to brush it off, only to witness her moaning with another guy on a different day.
Realizing that Akari was beyond redemption, Tatsuya decided on revenge…

[Translated from dlsite]