Mizuiro

Brother Kenji and his younger sister Yuki live under the same roof. Their parents are often away, and she secretly longs for her older brother. One day, though, a girl suddenly appears from the closet in Kenji's room. Strangely, her body is transparent, and she looks like a ghost. Her name is Hiyori, and it turns out she is a dear childhood friend. But when Kenji and Hiyori grow close, Yuki is shaken, and she remembers an unpleasant childhood memory: A much younger Kenji gets an unwanted ring from a toy dispenser, and will only give it up in exchange for a yo-yo. Desperate to be his bride and seeing the ring as a sign of that, Hiyori gets a yo-yo, but then has to leave town and move away. Hiyori gives the yo-yo to Yuki, to pass on to Kenji. But Kenji's ring was never given to Hiyori, and so a promise was broken. It becomes clear that the events of their childhood are connected to Hiyori's appearing now...