A Dog In The Sidecar (2007)

Kaoru (Matsumoto Kana) is just a normal girl living with her annoying brother (Taniyama Takeru), harried mom (Suzuki Sawa, Loft), and languid dad (Furuta Arata, Hana), until one day her mom just ups and leaves. Soon after her dad's new girlfriend Yoko (Takeuchi Yuko) comes strolling in. Kaoru isn't sure what to make of Yoko, who is brash, forward, good-humored, and at times downright uncouth. As the summer passes day by day, a unique friendship forms between them and Kaoru opens her eyes to a new, exciting world, even as reality begins to catch up. Based on Nagashima Yu's Akutagawa Prize-winning novel.