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

R-15 is about a boy, Taketo Akutagawa, who attends a school for geniuses: Inspiration Academy Private High School. Taketo is a genius novelist and writes erotica. Despite negative perceptions many people have of him, he aims to be at the top of his class and be recognized as the world's greatest writer.

In the midst of a violent invasion of Earth by unknown alien forces, photojournalist Wakatsuki Tetsuya comes across a scantily-clad alien woman, cutting a swath of death through the Terran ranks with her sword. After a chaotic struggle, Tetsuya is knocked unconscious, only to awaken aboard her starship. To his surprise, she turns out to be Kahm, the invaders' princess - and she has picked Tetsuya for a starring role in her upcoming wedding. As the groom...

10,000 years ago, acting as judge, jury and executioner, Dangaizer sealed the fate of mankind by reducing it to ashes. Slowly, mankind rebuilt their civilization and once again stands at its peak. Hiding amongst the survivors of mankind, the evil organization of Goma lies in wait for the return of Dangaizer. This time, it’s a race to stop the awakening of the 3 that can pilot Dangaizer and subjugate the world to their rule. Will the 3rd pilot learn her true destiny and awaken in time, or will the world find a new destiny in the hands of Goma?