In the real world? Yeah, sure, jealousy is killer in relationships and the more people, the more sources of jealousy. Hell 'that' jealousy often comes just fine from the two sources of insecurity and misunderstanding in perfectly faithful monogamous relationships. In fiction? I don't get it. Especially fiction which otherwise exemplifies a celebration of... well... sluttery. Here for instance. Guy is totally getting his wick wet in a dozen girls. But somehow it's preferable that he excludes all others for a single one at some point because "that's romance" isn't something I understand. Granted, I don't know where this story is ultimately going, NeonGhosts might well pair Guy off with a single girl in a way that works in the narrative, and thusfar that's more or less what I'm expecting. But as it stands that only seems to be really a thing with Ashe, and even then she seems open sexually to threesomes, and is more against the emotional infidelity. Which strikes me as realistic and pertinent to her character, but also ends up more or less forcing a choice where Guy has to decide if she's 'worth it' (along with sub branches of infidelity). which is where I'm going "nah, brah"
I at least understand the harem games where the MC is all like "I'm the only one you can sleep with, but I get anyone I want" without jealousy ever coming into play. Dickishly selfish it may be, it's fiction, and fictional people can be well fleshed out and deeply complex and be satisfying without being overly wishfullfillmenty. Like "WVM"s first two LI have absolutely workable motivations and justifications that can be woven into far more interesting and complex stories. (To be clear, WVM is not that interesting, narratively speaking.)