A film that reminded me a lot of the 90s anime where some young dude ends up with an unsuspecting girl crashing his room or apartment (think Video Girl Ai). The twist here is that the girl is in fact a ghost. A cute variation that offers some new giggles, but in the end it doesn't do too much to an overly familiar formula.
When Yohei and his girlfriend split up, a ghost takes her place. It turns out that she's been living there all along, but Yohei's girlfriend's strong aura kept her at bay. Yohei isn't too shaken by the ghost, even when she tells him off for treating his former girlfriend badly. The two get along well, and Yohei begins to fancy his new roommate.
Light romance and comedy, and a bit of plot to fill the gaps, that's what you're getting. The performances are okay, the presentation is proper but not too remarkable and the pacing is solid. It's certainly not the most memorable film, but the finale is nice and it passes the time quite well. Solid filler in other words.