Oσg!!! = Oh My God = summary:

Kanda, a salaryman whose miserable life seems to revolve around working overtime, comes across a murder scene on his way home one night. The murderer was covered in blood… and they turn out to be his former classmate, Lizzie! “It’s like a dream~” says Lizzie, before forcefully inviting himself into Kanda’s home. The sudden appearance of a contract killer gradually invades Kanda’s daily life?