寝取られ三角関係 ～初恋の幼なじみがセフレにされた～

The story centers around Sakagami Daichi, a salaryman at an insurance company, who has feelings for his childhood friend and first love, Matsuura Sakuya. However, Sakuya doesn't reciprocate these feelings. Daichi often spends weekends drinking with his friend Hori Ryouma, a sports club instructor. One day, Daichi wakes up to discover that Sakuya and Ryouma are in a romantic relationship, leading to a twist in their close friendship.