Chapter 12 is titled "Who and Why".
Furuta's attempt to kill Ata fails, leaving everyone helpless against him. Forced by his enemy to look at his own weakness, Hachimaru takes a hard look at the errors he's made. He realizes that he hasn't been acting like a true Samurai, and resolves to correct course by facing Ata alone in a bid to protect everyone.
Having barely survived Furuta's attempt to kill him, Ata levitates what's left of himself and moves to take Hachimaru. He swats Ann and Hayatro aside and slashes at Hachimaru, but Furuta takes the blow. Ata is angered at Furuta's persistence, and everyone else is enraged at his cruelty. Before he can move again, Ata is shot at by Hagamichi, who shaped part of his Holder into a gun. Ata scrambles to deflects the gunfire, annoyed that he can't deliver a long range slash in his condition. When he gets fed up, he triggers a bomb hidden in the hilt of one of the blades pinning Hagamichi down. Daruma's AI informs him that he's only fifty percent healed, and needs to get to sixty percent before he can move again. Angered at his slow recovery, he decides to go to sleep, which will decrease the recovery time to under three minutes. As he goes to sleep, he pleads for Hachimaru to hang on for that long.
Hachimaru tends to his badly wounded father, and remembers a time when he was young. At that time, he called for his father and he didn't come immediately, which made him cry. When he does show up, he explains that he went out to get allergy medication. Hachimaru admits he was scared he was gone forever, and Furuta tells him that he would always be there for him. He says that he wishes he would stop being a crybaby so he can leave the house without worrying. Hachimaru asks if there is medicine for that, so Furuta tells him that the key changing that is to act tough. Hachimaru still doesn't understand, so he clarifies: being tough is resolving to smile and laugh in the face of hardship. When Furuta tells him that acting tough would make him happy, he agrees to try it.
Snapping back to the present, Hachimaru apologizes to Ann for lying and asks her to watch over his dad. While Ann uses her sash to address Furuta's wounds, Hachimaru goes to challenge Ata. Ata stands amused, but Hachimaru is not backing down because he now understands Daruma's lesson about acting tough. He realizes that he's been acting tough for his own sake, forgetting what his dad taught him as a child. Drawing his Samurai Soul, he silently apologizes to his dad, and openly declares that he will protect everyone. Ata is unfazed by his words, thinking he is only showing off. Hachimaru declares that he's not showing off anymore and charges, but Ata easily pushes him back. He manages to stay on his feet while Hayataro rushes to shield him, but Ata easily slashes through them both. Despite taking heavy damage, he and his Holder stay standing. Ata continues attacking, but Hachimaru starts dodging him, and Hagamichi realizes that he's starting to anticipate Ata's movements. While he holds out, a barely conscious Furuta watches, remembering how weak Hachimaru has been throughout his life.
Ata manages to run Hachimaru through, but he stands his ground, recognizing that his opponent will get to Ann and Furuta if he loses any more ground. Ata reveals that Samurai, unlike humans, don't die from regular injury: they die when they accept defeat. When they falter, Fudo Myo-o forsakes them and they turn back into a Locker Ball. To survive, a Samurai needs an abundance of courage, something Hachimaru doesn't have. However, Furuta summons the strength to talk, telling Hachimaru that Ata is wrong about him and admitting that he is strong. Remembering his dad's lesson in acting tough, he smiles and listens to his dad apologize for his shortcomings. He responds that he will give acting tough another try and charges at Ata. His surge of courage takes Ata by surprise, allowing Hachimaru to slash him with his Samurai Soul.