Responses
the main couple go to a bunch of different universes with different settings for each. ch91-110 fits what you are askin for but idk of ur bothered to read everything else
https://www.mangago.me/read-manga/i_have_to_be_a_great_villain/
Specifically looking for the trope where either the MC or ML are either raised in a lab or end up there for whatever reason. Extra points for any about one of them being something inhuman like a merman, has powers/abilities, and such. Extra, extra points if most of the story is in the lab setting. Thank uuuu xoxo! (●'◡'●)ﾉ