Did you try contacting the previous owner/s and ask them?
To me it sure looks like someone (maybe a female owner?) purchased a "car tattoo" sticker somewhere and put it on themselves or had it applied by a professional to individualize their car. And that is why you won't find any information on the car about it.
What are you planning to do with it? Remove it? Or replace it?
Depending on how long it's been on there, if you remove it, the shape of the sticker might show on the paint. But you're lucky you have a black car that (on first glimpse) still seems to have pretty excellent paint. In case you want to replace it, you could go to one of these advertisement shops that put stickers on cars and have them print you a custom sticker that covers it up. If they're good they should be able to do that if they have access to the original on the car by taking photos and measurements.
But if it's really worth the money for you... well that of course is another question.
If you just want t remove it, then google a bit on tricks how to remove stickers on cars and how to make the paint blend in after. My first guess would be that if you manage to get it off without damaging the paint then - if you need to do anything all- it probably just needs a little polish on and around the area where the sticker is now, to make it look all perfect again. But professionals that apply these kind of stickers can surely give you better advice how to remove them, if you inquire about the cost to get a new one made.
