Diabolik Lovers, hands down. I'm probably much more invested in the series and the characters than I should be, and the same can be said for Ken ga Kimi, especially when it comes to Kei, but this is a problem I refuse to fix 8'D other ones that have ruin--I mean touched my heart are Black Wolves Saga, Dramatical Murder, Akazukin to Mayoi no Mori, PersonA Opera Za no Kaijin, Starry Sky (for the nostalgia as my first ever otome game series), Koezaru wa Akai Hana (this one has a briliant story if you can get past the not so stellar art), Dot Kareshi We are 8bit Lovers (they're fairly short games but absolutely hilarious and entertaining, worth your time xDDD), and a real gem that I've played is a Korean otome game called Dandelion Wishes Brought to You. The company who made it is just a baby, but man they certainly found their niche!