Bocchi no Boku ni Kyousei Kanojo ga Yattekita

On my 24th birthday, I come home to a girl asking to be my lover!! From middle school onward, I've been a "loner". I had no idea why this girl would want to be with me, but eventually it comes out that she's from my mom's company and she asked her to do this?! She says no to my mom= Mom is sad+ workplace is awkward... Now begins the story of two people trying to be in a fake relationship!

(Source: MangaPlaza)