In Pursuit of the Legitimate Heir

In Pursuit of the Legitimate Heir (狙われた正統継承者, Nerawareta Seitō Keishōsha) is the 23rd episode of the Kekkaishi anime adapted by Sunrise.

Summary
Gen destroys yet another Ayakashi that escapes Yoshimori, then leaps away. Yoshimori is about to chase him, but Tokine stops him and scolds him for not cleaning up the mess that Gen left. Yoshimori points out that Gen always leaves them to clean up the messes he makes, then gets in a fight with Madarao for pointing out the exact number of times it's happened. When Hakubi points out that Tokine isn't happy with the situation either, she decides to have a talk with Gen the next day.

At school, Yoshimori and Gen pass each other without speaking (though Yoshimori glares at Gen's back). Gen gets an unexpected visit at his apartment that evening from Kyoichi Hiba, who reminds him again to stay in control. Gen assures him that there's no problem. At Karasumori that night, Yoshimori plots to attack Gen, but Madarao reminds him that he has bigger issues to worry about. Tokine tries to talk to Gen, but he runs away before she can.

Madarao leads Yoshimori into the school, reminding him along the way that as long as he keeps his cool, they should have no problem catching the Ayakashi before Gen. In a hallway they find Ookubiguruma, a rolling Ayakashi with retractable spikes that rips through the first Kekkai easily. Yoshimori is preoccupied by the damage the Ayakashi causes (since he knows he'll be the one to clean it up again) and only dodges until Gen arrives. Gen manages to match the Ayakashi's rotation speed and force it outside. But Ookubiguruma reveals its spikes while Gen is clinging to it, slashing him deeply and sending him flying toward the ground. Yoshimori attacks the Ayakashi while Tokine catches Gen with a Kekkai. She stops Gen from getting up, since she's confident that Yoshimori can handle things. Despite this, Gen's wound heals quickly, and in moments he's back on his feet.

Yoshimori keeps using Kekkai until he finds the perfect amount of strength to slow the Ayakashi down, so he can hit it with another Kekkai. Seeing this, Gen realizes that Yoshimori is a rare type of fighter than can change his techniques in the middle of a battle, and that Masamori assumed they'd get along because they approach battle the same way. Yoshimori is surprised when Gen returns to fight despite having been injured.

Hakubi reveals that Gen is part Ayakashi, and his body heals much faster as a result. He notes that Gen must have excellent control over his power to use so much of it in Karasumori without running wild. Yoshimori overhears Ookubiguruma mention a bounty on his head. He drives the Ayakashi into the school so it has less room to move, then uses a Kekkai to keep it from spinning until he destroys it. Gen realizes that Yoshimori fights on pure instinct. Hakubi and Gen suspect that the bounty must only be on Kekkaishi, and Yoshimori figures the same Ayakashi group is behind it. Gen tries to leave without cleaning up, but after getting protests from Yoshimori and Tokine, admits that he only knows how to destroy. Tokine lets him go, but sees that Gen is insecure around her, and is more hopeful that they can get along in the future. Yoshimori finds Gen relaxing in his favorite rooftop napping place the next day, and they reluctantly share the space. They begin to discuss Gen being part Ayakashi: Gen only notes the downside, but all Yoshimori can see are the benefits, and he admits he's jealous. Though they don't agree, it's one of the first real conversations they've had since Gen's arrival.