Black Sage was behind the explosion at the end of Volume 17. The public starts to blame magicians for the bombing attack. (Heigu apparently used a corpse instead of a living person to infiltrate their meeting location). Return of the anti-magician propaganda, Ten Master Clan decides they need to get to the bottom of this. Tatsuya, Juumonji, Masaki and Mayumi team up to hunt down the Black Sage. Soon, Tatsuya and the others may go ahead feared course/direction/way. When Tatsuya is near to grasp the clue leading to Heigu's whereabouts he is blocked by an unexpected opponent.
Gouki say to Masaki : Yotsuba-ke's Shiba Tatsuya-dono is equal to you, he'll join to the search under Juumonji-dono's leadership. Masaki, show your will-power. Pushed by Gouki, Masaki tries something unexpected to try and get close to Miyuki and Mayumi also is being pushed to the forefront by various schemes not her own. Meanwhile the emotional battle continues.