AMOR VINCIT OMNIA

so you know how in genshin impact (if you ever played it), there are beings called descenders who transcend the laws of teyvat and are able to influence its fate?

well, i like to think of isekai'd non-mc as a "descender". you are not native to the world of LADS and as such, you are immune to the general laws of this world.

i'm not sure what other rules you can bypass just yet but one thing is for sure: you will not bend to the MC nor the LIs' will. you act independent of them and thus, form your own connections and feelings on every matter. you will find that you're generally immune to each of their charms and when you do grow fond of them, it's likely because your relationship with them naturally blossomed overtime. yes, even if you know them intimately because of being an avid player of the game. (now i imagine this will be even more fun for non-mcs who are generally clueless about the plot!)

now, the fun part: you are a descender. you can challenge and even change fate. if the MC and the LIs are destined to be together because of their past lives, bonds, soulmate connections or whatever... that matters very little to you. to everyone's surprise, you slowly worm your way into their hearts, whether they like it or not.

it should be impossible. MC should be the only person in their hearts 'til the end of time but here you are, challenging what they've always believed in. all of a sudden, they can't stop thinking about you. when you're not around, they wonder where you are, what you're doing, and who you're with. (though let's be honest, depending on the LI, they're most likely already keeping tabs on you.)

they still love the MC, of course. that will probably never change but to think that someone like you can come around and make them falter, make them feel things they've never felt for anyone else but their beloved is genuinely unthinkable to them. honestly, among other things, that's part of why they're fascinated by you.

this could add some tension though. perhaps the LIs understand that they're all connected to the MC so there's the assurance that they will always find each other in every lifetime no matter what but you? you can easily slip away from their grasp. you don't belong here, that much is certain, but they want you to. god, they hope you do. even if you stay, you could easily drift into another world. a world in which they cannot follow, not without a mark or a bond or a pact or something because they cannot impose their will upon you. you cannot be tied down. you cannot stay even if you wanted to. there is no telling where the cosmos will take you next.

all they have is their love and affection but it's not enough. they need more to convince themselves that this is real and the two of you will always be together.