Alternate universe. Dungeons (portals) pop up randomly with monsters. Espers (basically superheroes) go in to fight in these dungeons and when they defeat the big boss the dungeon will close and people will be safe. But oh no esper is damaged and weak now because of fighting, so they need a ‘Guide’. Aka someone who can heal them with touching/being nearby. Faster healing with sex yay
Different yaois will have different guideverse rules, but these are the pretty basic ones I believe. There’s also rankings so higher ranked espers are more powerful and usually require higher ranked guides to heal

can someone explain guideverse to me in layman’s terms?