My (Childhood Friend) Girlfriend Was Cuckolded by the Protagonist! Well, I’ve Known This for a Long Time

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 problem with my ex-girlfriend …

This is the story of me, a supporting character, surpassing the protagonist.