Split Personality: We’re All Crazy, Hahaha, We’re All Crazy

Two male leads + older man/younger man + alternate world + beast world + interstellar

I don't recommend reading this one if you're looking to drop it. Flins is an original character, not the one from Genshin Impact.

After his beloved died, he went mad. He went mad, and he went mad too!

An accident brings a long-buried secret to light, but why has everyone gone crazy?

Note: The main couple features an older man!!! The main story is entirely free of infidelity.