Help. I had read the first chapter of this series over a year ago. About a male highschool MC. He met a girl that is suffering from a curse. From what i remember she was about to die because of her condition. Her body was rotting(im not sure) or some kinda death curse. She asked MC-kun to kiss her (or have sex, im not sure) because its the only way for her to survive. Theres another girl I think it was MC-kun's sister, shes a brocon and a yandere..

Thanks in advance! 😀

Umm... the first thing I thought of was Sakuranbo Syndrome but it only fits with the "rare disease" and "kissing"