Rehabilitation Training

After the extensive mission on Mount Natagumo and battle with members of Rui's family, the Demon Slayers Tanjiro Kamado, Zenitsu Agatsuma and Inosuke Hashibira all suffered extensive and severe injuries. After being rescued by the Hashiras Giyu Tomioka and Shinobu Kocho, the three were treated in the hospital ward of Shinobu's estate, the Butterfly Mansion. After their initial recovery was finished, they were required by Shinobu to undergo Rehabilitation Training in order to fully heal their bodies for upcoming missions in the Demon Slayer Corps. Through three unique sessions and extensive, lengthy training under Aoi Kanzaki and Kanao Tsuyuri, the three Demon Slayers were once again in top condition, and even became more powerful after learning a new technique.

Stretches
The first part of the training methods used in the Rehabilitation Training was stretching. and the task was accomplished by Sumi Nakahara, Kiyo Terauchi and Naho Takada. Naho and Sumi would hold down and brace the boys' legs while Kiyo would pull back their torso through their arms. This aided with regaining flexibility and makes the bodies limber for training; an important strength that is accentuated by the fact that the trio had spent much time in bed. The stretching session is shown to be quite rigorous and painful, evident by the usually flexible Inosuke crying visible tears through his boar mask upon being stretched out.

The only person who had not felt pain was Zenitsu, who was shown laughing when the three girls were in the process of making his body limber, simply because he enjoyed the feeling of being touched by girls.

Reflexes test
The second part involve honing their reflexes and improve them; since their in-bed recovery was slow and lengthy, their reaction speed would have likely decreased considerably, being in the secure Corps' Headquarters and not out on a mission. The test was performed by both Aoi and Kanao, with the latter being the main challenger to defeat.

On a table with cups filled with medicated water, the object was to pick up and splash Aoi or Kanao before they could do so in return. However, both challengers are allowed to block the chosen cup and prevent them from throwing it, leaving the opponent to pick up another before being hit, or block the incoming cup to then make them pick up another.

Since Tanjiro seemed the most willing to improve initially, Kanao was his opponent during most of his training; Aoi was initially Zenitsu's and Inosuke's. Soon, the two were able to beat Aoi, leaving Kanao as their new opponent.

Full-Body training
The last part involves what is essentially an enhance game of tag, with the objective being to grab the opponent attempting to escape. The opponents again were Aoi and Kanao, with Kanao again being the final goal to achieve. As with the previous test, Zenitsu and Inosuke were able to beat Aoi rather soundly, which left Kanao as the new opponent.

Total Concentration, Constant
Initially, Kanao was unchallenged by none of the three, owing to both her mastery of Total Concentration, Constant, and her more extensive training and skills as Shinobu's Tsuguko. Zenitsu and Inosuke became downcast and were unwilling to continue rehabilitation just to be beaten, leaving Tanjiro as the only one to push onwards. Wanting to know how Kanao was so ahead, he was told by Sumi, Kiyo and Naho about her usage of Total Concentration throughout the day, as well as the fact that all the Hashira have mastered it, given them the physical advantage over normal Demon Slayers. Tanjiro initially attempted to do so but failed, because of the incredibly taxing exhaustion on the body when using it for long periods. Nonetheless, he persevered and used his knowledge of Sakonji Urokodaki's teachings to help him improve lung power. He was then told of a technique involving very hard hollow gourds, with the aim being to break them just by blowing into them. After seeing the large gourd able to be broken by Kanao, Tanjiro became greatly motivated to persist and master it, even enlisting the girls' assistance to help him maintain his breathing while asleep. Eventually, Tanjiro was able to keep up with Kanao; though she was still undefeated, even she was surprised by the speed he managed to improve at. He is then able to break open a small gourd, and his success was seen by Zenitsu and Inosuke. Wanting to improve as well, they consulted Shinobu, who told them about what he is trying to accomplished. Though confused by his explanation, Shinobu's way of saying the technique is simple and through unique motivations, Zenitsu and Inosuke became driven to master Total Concentration, Constant as well. They adopted the drills and techniques Tanjiro had been using and motivated each other in order to help the other improve, getting stronger as one

After successfullu maintaining Total Concentration without stopping at all, Tanjiro became the first to beat Kanao in both the reflexes test and full-body exercise. Seeing his triumph, Zenitsu and Inosuke pushed themselves even harder to reach him.