Thank you for the update! I'm sorry to hear it was such a busy week. Awesome hearing news about the many research and resources, the developing game sounds exciting!
If this helps, a good example of a yandere is Toma from Amnesia, Lizzie from OMG!, various guys from Diabolik Lovers such as Kanato, Masato from MOSHI, KONO SEKAI NI KAMISAMA GA IRU TO SURU NARABA (masato is tw for incest, and all these guys are tw for gore and disturbing behaviour). In the game Obey Me, some of the demon guys show hints of a yandere side like Asmodeus for example. There's also the mc from Happy Sugar Life, she's a bona fide yandere archetype.
Tbh i forgot a few of the ones I know so i google searched to remember my sources.
Hananoi kun is like the more sfw version as he's mainly deeply insecure and is trapped between wanting to control the mc because he doesn't want to use her, and learning to value her feelings instead of forcing his abandonment trauma onto the mc. Sorry, i forgot the rest but there's some great forums discussing yanderes in otome, anime/manga