What I still remember is that it's a full color Manhwa/webtoon and it's not shoujo/jousei but more shounen or seinen.

The prince is a blond that looks very much like MC and is supposedly evil or will become evil in the future but currently sees something in MC because of his abilities.

There is a beach/island arc where MC and the prince together with some others are camping/surviving.

The story is in an academy setting so alot of school.

I believe that the princess should have died very early on before the game story but because of MC she survived and is now a wildcard.

Also I remember during the beach/island arc a girl from MC's team was going out of the camp at night and when MC asked where are you going she reluctantly said she had to poo in the bushes to which MC offered here a pan of seawater

I think you're talking about Demon King of the Royal Class

Yeah, that's it. Thanks man.