Like Someone in Love(2013)

When Akiko, a lovely Tokyo student who moonlights as a call girl, is dispatched to a new client in the suburbs, she is surprised to find the shy and elderly Takashi, a committed academic constantly distracted by work-related phone calls. The lonely widower seems far more interested in playing house than having sex, however, and the young woman soon falls asleep. The next day, when the two encounter Akiko's volatile boyfriend Noriaki, Takashi plays into Noriaki's assumption that he is actually Akiko's grandfather. As the three settle into their new roles, Takashi finds himself becoming the protector that Akiko so desperately needs.