Living Game

From Prisms:

A romantic comedy about Fuwa, a guy living in a small apartment in overcrowded Tokyo, who wants to have a place of his own. Because of a building accident in their new office building, Fuwa's company (5 employees) had to move into his apartment, right after he had moved to a larger place. And the new employee (Hiyama Izumi, a 15 year-old girl) had to move into Fuwa's place, as she had just come from the country. Then Fuwa's old girlfriend Tokiko, who had already gotten married, ran away from her husband and came to Fuwa's place.