http://www.mangago.zone/read-manga/kawaii_akuma/ (this mangakas seme are usually a bit yandere)
http://www.mangago.zone/read-manga/oshiete_katekyo/ (if you don't mind bara)
http://www.mangago.zone/read-manga/houkago_no_love_call/
http://www.mangago.zone/read-manga/love_monster_mio_junta/ (a bit yandere)
http://www.mangago.zone/read-manga/boku_no_kichiku_megane/
http://www.mangago.zone/read-manga/katekyo/ (a bit yandere)
http://www.mangago.zone/read-manga/akanai_tobira/ (can't remember if it's the seme or uke whose yandere in these one-shots
Wah! Thank you Kathy ! =))
Tks !! (ﾉ≧∀≦)ﾉ
Some more I just remembered:
http://www.mangago.zone/read-manga/itoshii_akuma/
http://www.mangago.zone/read-manga/houkago_no_love_call/
Yaoi manga with yandere seme ? :D