Episode 37

Tonight (今夜) is the 37th episode of the Kimetsu no Yaiba TV anime series, and the 11th episode of its second season.

Synopsis
After his encounter with Upper Six, Daki, Zenitsu is sure that she is a demon; however, Daki also realizes that he is a member of the Demon Slayer Corps. Shortly after, Zenitsu disappears. Tanjiro and Inosuke, who have gathered for their regular meeting, are notified of Zenitsu’s disappearance by Uzui and told to leave the Entertainment District.

Plot
In the Tokito House, Koinatsu's young assistants ask her to read them books. Before she does so, she graciously gives the two treasured hirauchi kanzashi hairpins meant for her, saying she wants them to have it. Elsewhere, in the Kyogoku House, a chaperone informs the owner that "Zenko" is missing. But the owner angrily refuses to let them search for her, not wanting to do anything that might upset Warabihime. Above the district's rooftops, Tanjiro and Inosuke discuss their situation; Inosuke informs him that there is a demon in his house but his unusual way of describing it only confuses Tanjiro. Without warning, Tengen joins them and states that Zenitsu will not be arriving.

When Tanjiro asks what he meant by that statement, Tengen only tells them of his regret in making them join him in his mission; his want to rescue his wives has led to Zenitsu going missing. The Sound Hashira dismisses the younger Demon Slayers, as he believes them incapable of handling an Upper Rank demon, should they face it. When Tanjiro tries to voice his support, Tengen only tells him there is no shame in leaving the mission before vanishing from the two. Tanjiro believes he thinks so as they are the lowest rank, only for Inosuke to inform him they have in fact gone up, the three now three up from Mizunoto to Kanoe. Inosuke then displays his rank by flexing his arm and saying his rank, the mark appearing on his forearm. Told he has one too and that it is a sign they are now Demon Slayers, a remotivated Tanjiro tells Inosuke he must wait for him so they can start investigating the Ogimoto House together.

Inosuke disagrees, leading the two to quarrel until Tanjiro clears up his statement by saying the demon in his house is still nowhere to be found and Zenitsu is still missing, believing there is a passageway between the three houses allowing the demon to travel between them. Tanjiro adds that he thinks the demon has disguised itself as a human and it would be careful about killing people to prevent blowing cover. Inosuke concurs, as a murder and bloodshed would be difficult to clean. Due to the district's nightly activity convenient for demons, he believes Zenitsu and Tengen's wives are all still alive. With the plan set, Tanjiro tells Inosuke to look for them and stay alive, Inosuke agreeing to the terms.

In the Tokito House, the girls give Koinatsu her tea and she dismisses them for dinner. Left alone, Koinsatsu is suddenly joined by Tanjiro, re-equipped with his uniform and Nichirin Sword. He gives her his payment for the master during his time spent in the house. Seeing her surprised by his uniform, Tanjiro informs her he had to be disguised, only for Koinatsu to tell him she knew all along he wasn't a girl, to his shock. Tanjiro tells her he will be rescuing all who have gone missing. The Oiran visibly relaxes at his words, as she will be leaving the district to be married, to Tanjiro's joy. She mentions she had worried for the missing as she is about to leave, telling Tanjiro to stay safe and not disappear too, Tanjiro bids her farewell and wishes her happiness; she thanks "Sumi" and returns the sentiment.

As she continues preparing, she hears something and asks if he had left something. Instead, Daki appears before the young woman, telling her she won't forget to devour her before she leaves the district. As Tanjiro runs to the Ogimoto house, he pauses and detects the scent of a demon nearby. In the Ogimoto House, Inosuke becomes angered at Tanjiro not joining him, deciding to take action instead. He jumps up, slams his head into the ceiling and commands "Hey mice! My swords!". In the shadows, two Ninju appear, holding Inosuke's blades and walking towards him. Inosuke compliments Tengen for training the mice as his personal servants to call upon. Re-armed, he bursts out his room to battle, to the surprise of a nearby chaperone.

In the Kyogoku House, the owner stares at his wife's bloodied kimono only to hear a voice ask about Zenko and Hinatsuru's whereabouts. Tengen appears and threatens the man with a kunai to the neck. Terrified, the owner only states that Zenko had disappeared and Hinatsuru had fallen ill and was taken to the Kirimise, the poorer section of the district. Tucking his blade, Tengen tells him he can be trusted and asks for everything he knows. The owner tells him of the oiran named Warabihime, in the room on the north side without light. With his information, Tengen disappears and leaves the man bewildered at his sudden visitor. Entering the room and seeing it empty, Tengen surmisses the demon is now hunting and runs across the district roofs, heading to where Hinatsuru is likely at, reasoning she might still be alive and with information. Tengen believes the demon should return to the room during daybreak, declaring he will kill it.

Returning to the now dark Tokito House, Tanjiro opens the windows to warn Koinatsu. Instead, he meets Daki. She asks if he is a Demon Slayer, then asks how many of them are there, knowing Zenitsu is one. Unanswered, she asks if there is a Hashira with them, believing Tanjiro isn't at a Hashira's level, as she stares at Koinatsu absorbed into her obi. She turns to him and says she never eats dirty, old or ugly people. Tanjiro sees the kanjis in her eyes and realizes she is Upper Six. He draws his blade and demands she let Koinatsu go, angering Daki. She swats him away with her obi, sending him into a nearby house.

Stunned by the impact, Tanjiro takes a moment to will himself to fight and gets up, steeling his resolve to face her. He realizes her main weapons is her obi; with the ability to absorb people, he realizes it's the reason he was unable to find a secret path big enough for a human, since it only needs a thin crack to pass through and absorb someone. Daki sees he survived the impact, before complimenting his eyes, saying she would gouge and devour them later. The strap holding Nezuko's box breaks, leading him to set it down. Tanjiro tells Nezuko not to leave the box unless her life is in danger. Using Water Breathing, Fourth Form: Striking Tide, Turbulent, Tanjiro leaps into the air to face her, Daki retaliating by sending her obi sashes. Tanjiro attempts to cut them but the obi initally prove too durable for his blade.

Eventually, he slices one but Daki punches him towards the ground. As he slow his fall, Daki lands down too and compliments him for his decent mid-air battle, as well as for seperating the one sash containing Koinatsu. As he tries to regain his breath, the demon comments of her fondness of him. Trying to realize he is now facing Upper Rank Six, Tanjiro reasons whether he can battle her without Tengen, Zenitsu or Inosuke. He then declares it's not a matter of could he do it but that he has to do it. Raising his blade, he prepares himself to face Daki alone.

Characters in Order of Appearance

 * Koinatsu
 * Tanjiro Kamado
 * Inosuke Hashibira
 * Tengen Uzui
 * Zenitsu Agatsuma (Mentioned)
 * Daki
 * Hinatsuru (Mentioned)
 * Nezuko Kamado

Anime Notes

 * The pre-opening scene of this episode is an anime original scene that adapted a page of the Volume 9 extras.
 * This is the last episode to air in 2021.