Shoujo Jihen

Fena is a girl who has lived her whole life as an assassin. Her next target is Eve, the manager of a café. One night, she ambushes Eve in an alley, but her attack fails, and she is recruited to become a waitress at the café instead. Confused about Eve's intentions for hiring someone who just tried to kill him, Fena takes the job in order to kill Eve at the next opportunity. A hit girl and a café manager—their fates intersect in an intense noir thriller.

(Source: Kodansha, translated)