Haeran, The Chemical Engineer summary:

Hae-ran wants three things. Good health for her grandfather, one meal per day, and a masterpiece of a lifetime. In front of her appears a potter named Hwaseon (畵仙) who can grant all three wishes. “Be my chemist.”This will be the beginning of a sad fate... The story of Hwaseon Ye-an, who wants to end his immortal life, and Hae-ran, the only person who can kill him.---- (https://manga.line.me/product/periodic?id=Z0001444)