In the Thirteen Years of Mizuki Ashia, the Japanese girl who grew up in America first saw Izumi Sano jumps high on TV. Surprised by his grace, Mizuki quickly became a big fan of Sano. Three years later, Mizuki, who studied in high school, decides to return to Japan, so that one of his dreams come true: to see how Sano jumps personally. Mizuki even goes to Sano's school, hoping to be closer to him. She satisfies the desire of Mizuki and becomes a neighbor on Sano's room. However, there are two problems: Sano refused to jump in height, and he visits the school for boys, which means that Mizuki now has to dress as a child in the morning, at noon and evening, even in her room! However, not knowing Mizuki, Sano quite quickly detects its secret, and now weird feeling took possession of both ...