According to Kadokawa, an OVA of R-15 will be bundled with the tenth volume of the novel.

Yuji and Koichi set off on a journey to find a rare bamboo flower for a school project. In the forest they encounter a legendary phoenix who asks for their help to save the forest.

One day Kan-chan finds a magic bottle in the attic. Whenever someone sneezes, a genie named Hakushon Daimaou is brought out and must grant any wish of whoever sneezed until he or she sneezes again. Sometimes, however, he accidentally fails and only causes trouble instead of granting any wishes.

Two neighboring childhood friends. An airheaded girl and the boy who takes care of her like a mother hen. And of course, there is his family background with a tiny, insignificant supernatural secret. Now that her parents have left the girl in their neighbor's care, will she ever discover her friend's secret?