Tensei Last Boss Majo wa Doku Potion de Kusuriya wo Hajimeru

A sickly high school girl reincarnated as the ultimate witch boss!? Now that she's healthy, Matilda is ready to give up her dream of becoming a great witch and enjoy a slow life in the frontier! Using her special ability: poison potions, she opens a pharmacy. However, the one who shows up is Leo, the scheming hero who plans to condemn her in the future!?

(Source: Manga Park, translated)

Note: All chapters were split into multiple parts in the original serialization and later combined in the volume releases.