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!!