oh god please not yuno from mirai nikki, she's a standard generic yandere that isn't necessary a good example for a dateable character - if i may suggest a good example of a yandere, i'd suggest Zahid from Please Don't Eat Me and Dylan from Taming of the Tyrant which are both webtoons. One of them gives the feeling of dancing on the tip of a knife and the other feel almost like a green flag until you see all the red and that's a good way to play with yanderes as opposed to just red flags abroad from the start IMO

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

Some of my favorite webtoons/manga that have yanderes involved are Secret Alliance, Dreaming Freedom, & Firefly Wedding. Some other yandere games on itch I liked include Karamu by Chattercap, Sweetest Valentine by sylvan, My Darling by WaterHorseGames, Binary Star Hero by CONCRETEPARASITE, & Solipsism Reigns by Melancholy Marionette. There are a lot of cool yanderes nowadays, I hope you can find some good inspiration!!

Restart Heart tho not fully implemented is full of yandere flavors, Nameless: The One Thing you Must Recall has a couple, many of the manga if you google those w/ obsessive in the title(even if only fan-translated) have a bit. There's yan-goodness in The Kid at the Back, too. Some of the characters in Princess of Ruin get some yan-tendencies and paths(depending on your choices).  Also the tumblr "maleyanderecafe" has some good examples and games to try and such.

I'd personally not go off Mirai Nikki so much as a ref since not always but in general male and female yanderes have different tendencies. I've noticed male ones're less stab-habby/outwardly violent towards the person of their affection(maybe because violence against women is too real/deepseated in some ways?) but obsession, jealousy, drugging and/or locking up "for their protection", handling obstacles/threats to their love, etc are a lot more common.

*ETA* Oh yeah Melancholy Marionette's games often got some yandere flair to them.