Nao is a Japanese American girl who recently moved to Tokyo with her father, and struggles with bullying, depression and her stilted relationship with her dad, especially once he loses his job and sinks into depression. 
After a tsunami, her diary washes up on the shores of an island off of B.C., Canada, and Ruth, a Japanese Canadian author, starts reading it and trying to piece together what happened to Nao and where she is now.

The book blends magical realism, Zen Buddhist themes, and some wacky multiverse time travel stuff and while it gets dark (graphic violence in bullying scenes, attempted rape, a lot of suicidal ideation, heavy scenes from WWII-era family history), there's a hopeful ending and the ride's worth it