Bloody Sugar wa Yoru Warau

"Nega"—It is a bizarre disease that develops by acting on the negative emotions of human beings. Symptoms vary from person to person and cannot be seen by ordinary humans. Church and Jed are unalike brothers whose livelihoods are doctors who specialize in "Nega." The two are looking for a "certain nega" for their beloved sister, Basil...!? A dark, sweet fantasy presented by the most notable writer, Matsuri Midou!

(Source: Coamix, translated)