~otherworldy stories~

it'n's not an actual isekai but it's similar.
There's another version of the story but I don't really like it.
He was dumped for the hero because he's weak. He travels to get stronger (he can even defeat the dragon king) then he meets new love interests but is dumped (they realize only later that they love him). He returns with a friend to the Royal Capital but is involved in the succession fight and the fight against demons and so on.

He wants to fight the demons, but for him it's just a game: he was joking! The demons exist and his group fights them. Many unexpected events happens.