Chapter 20 is titled "Partner".
As Hachimaru celebrates scoring a point in the duel, Ann has to patch him up because he rendered himself helpless. Daruma takes the time to elaborate on the healing powers of a Samurai. The duel ends and Hachimaru tries and fails to get Ryu to open up about himself. The group arrives on Kenka just before the host of the competition places a barrier around the planet to trap the contenders inside. Once they reach the ground, they take down several opposing Samurai and learn they arrived late to the party.
Though in pain from beheading himself, Hachimaru is happy to have scored a point against Ryu. He then realizes that he cannot move and asks for advice on what to do. Daruma has his AI upload video of the round into his mind while Ann and Hayataro rush to his side. Ann rebukes Hachimaru for going overboard to win, but he counters that he is willing to push himself in order to become a match for Ata, an ideal that worries her. Having reviewed the data, Daruma commends Hachimaru's ingenuity, then tells him that decapitating himself is not a move he should try again unless he has companions who can reattach his head afterward. While Ann reconnects him to his body, Daruma offers some advice: if given the choice between reattaching a severed body part and letting it regenerate, go for the former option because it is takes less time. He warns that regrowing a body from the neck-down takes hours, during which time he will be helpless, leading to defeat in a real battle. Hachimaru asks if his head will regrow from the body or if the body must grow from the head. Daruma tells him that since the Samurai Key powers the healing process and is located in his head, his head would grow a new body and the old body will turn to dust on his own.
At that moment, Hachimaru's severed arm regrows while his old one disintegrates, and Ryu decides that though Hachimaru is nuts, he likes him, something that bothers Kotsuga. Hachimaru praises his strength and asks why he has two Samurai Souls instead of one, but Ryu already forgot about his two souls. After having it pointed out, he says that he does not know. He then begins asking about his abilities, fighting style, and who taught him, but Ryu can't answer. He then asks Kotsuga for information, but he knows as much as them since he's only had Ryu with him for a month. Ryu explains his amnesia and that he is traveling to discover his identity. Hachimaru asks why he accompanies a jerk like Kotsuga - who gets angry at the remark - but Ryu believes he is good. While Kotsuga flirts with Ann again, Hachimaru asks about Ryu's Princess and Holder, but he has no clue what either of those things are. Kotsuga then snaps at him, arguing that amnesiac or not, Ryu is entitled to secrets and that there are things people don't wish to remember. Thinking about when he apologized to Ann for lying about his childhood, he apologizes to Ryu, who decides he now likes Hachimaru as well.
Daruma then suggests they break for lunch, and Kotsuga gets miffed when Hachimaru quickly switches his thoughts to food. While the group goes to get food, Kotsuga holds Ryu back and warns him not to get attached to the others, as they may become enemies. On top of that, he aims to steal their stuff if they get killed. Hachimaru hears them talking, so Kotsuga plays it off by suggesting food to eat, winking at Ryu to signal him to lie. Hachimaru accepts the suggestion and leaves, then Ryu asks what a wink is supposed to mean. Kotsuga explains that it means he should keep their plan a secret.
The band then eats lunch, but while Hachimaru and Daruma wolf down Ann's dish, the two ronin are put off by the food's unappetizing look. They then arrive at Kenka and Ann takes note of the massive trenches carved into the planet. Kotsuga explains that the host of the battle royale does this to mark the content's location, which changes every time. Hachimaru is amazed at the feat and wonders if the host is the next Key they need. As they land on the planet in a set of ruins, they are spotted by a Samurai, who gives order to surround the newcomers. Hachimaru and company exit the ship, and Daruma has his ship set up a cloaking field for security. He asks Kotsuga for directions to the site of the competition, and while he looks, the host has a cloaking field placed around the entire planet. From the satellite orbiting Kenka, the host - a masked samurai and his Holder - watches the contenders. On the surface, Hachimaru notices a monitor with a number on it appear next to him Daruma, and Ryu. Daruma realizes that they are ID monitors meant to mark Samurai fighting in the battle royale after Ann notices she does not have one. Kostuga gets frustrated when his map fails to sync up, which Daruma suspects is a deliberate act.
At that moment, the Samurai who watched the group land charges Daruma from above, exclaiming that the battle royale has already started, as five other Samurai and their Holders charge in. Hachimaru instantly gets in front of Ann, draws his Samurai Soul, and assesses the situation. He deduces that his master will take down the Samurai above them, and three foes are in range for Ryu to cut down, leaving two for him to handle. Putting his new goggles in place, he steels himself and cuts his two foes down. Though pleased, he then notices as the number on the ID monitor decreased by the number of Samurai his group defeated. Back onboard the satellite, the host comments that the battle royale has truly started.