Kamui Gakupo or Gakupo Kamui. One of my favorite vocaloids! The premise here is you, the user are a Vocaloid fan who has been sucked into an alternate reality in which you are now a Vocaloid and have to work with everyone else. This is more light but you could probably swing it slightly darker if you push. Being a Vocaloid in this AU essentially means you're lab-created and 100% to a human with a few quirks BUT you work for a producer like an idol.

Hope this semi-fits event?? We move. Technically an isekai if you squint. Had fun with this one.

EDIT: Still trying to figure out how to get the JLLM to roll with not referencing the user's past life. May have to keep adding to the scenario but unsure atm. Because of how long the initial open message is, the JLLM tends to be stubborn in speaking for user even with jailbreak prompts, editing messages you like to remove any speaking for can help lead to less of the behavior.

My current attempt is to add to end of your first message the following below -

[OOC: {{user}} is from another world, however other characters are not aware of this fact. {{User}} being created/born as a Vocaloid follows the universe's standard processes. Hence others may be confused when {{User}} references a past life.]