Need help to find a manga

[One-Era]

I really need help to find this mangas title , the mc is stuck in a survival game where he finds out the ml is a returnee and he uses him . He seems kind of evil and has a harem? He just uses everyone but seems heroic in eyes of mc

 

[Reiru]

I really need help to find this mangas title , the mc is stuck in a survival game where he finds out the ml is a returnee and he uses him . He seems kind of evil and has a harem? He just uses everyone but seems heroic in eyes of mc

Fairly sure it's this one Regressor instruction manual , it's a manhwa not manga