Watashi no Kouguchi-Sensei

A self-proclaimed college student, Karen Shiina, suddenly shows up at the door of Ruri Koguchi, an up-and-coming Loli-style manga artist, to apply to become his assistant. But she has her own secrets and an ulterior motive. A workplace romantic comedy between an ero-manga artist and a college girl!
(Source: ComicWalker, translated)