The time is Heian, and 13-year-old Masahiro is the grandson of the rare yin-yang master Abe no Seimei. Still only half a man, Masahiro is still training to surpass his grandfather, while being teased by his partner Mokkun, the Mononokai. Then, there is a commotion in the Inner Palace, and Masahiro and Mokkun start their own investigation, but a strange shadow lurks behind the scenes. ...... Can the loser Onmyoji save the capital? The story of the struggles of the Heian Ayakashi, depicted by Sorakura Shikiji with his overwhelming drawing ability, begins!