私の（幼なじみの）彼女は主人公に寝取られた！まあ、このことはずっと前から知っていたんだけどね。 (Associated Names)

This world was a shitty game. And I was the side character who got cuckolded by the main character. So I moved according to the setting, not against the game, and finally, the protagonist cuckolded my (childhood friend) girlfriend. Now I could freely fall in love. I thought. But it seems that I have a…