Oda Aya manga
From Panda Scans: Sanjou Arashi is a serious and reliable 2nd year high school student working part-time at a detective agency. Her boss is a gambling, irresponsible, tobacco smelling oji-san. The pair are complete opposites, but this is the story of a scruffy oji-san X high school girl romantic comedy!
My Little Robinson is about a girl named Ichigo who struggles to balance her job as a successful magazine model with her life as a normal high school student, and a young man named Tsugumi who is a member of a race of humans who only grow to be about 15 cm tall.