Houkago Hokenshitsu, Kuro Bara Alice Recommendations
By the same author, both series carry a similar dark theme to it & intriguing storyline. Psychological aspects are evident in both series & romance for the main lead is a battle of logic vs emotions.
From the same creator and with a similar dark fantasy feeling. Kuro Bara Alice is the better work (since it's more artistically mature), but both are outstanding manga and very recommended.