The ongoing full-series rerun of Kimetsu no Yaiba (Demon Slayer) aired Episode 12, “The Boar Bares Its Fangs, Zenitsu Sleeps,” on June 21, 2026, sending fans into a frenzy online — particularly over the moment they had been eagerly anticipating: Agatsuma Zenitsu’s awakening.

About Kimetsu no Yaiba

Based on the manga by Gotouge Koyoharu, the series follows Kamado Tanjiro, a boy who loses his family to demons and joins the Demon Slayer Corps to find a way to return his demonized sister Nezuko to human form. The manga’s 23-volume Jump Comics run has surpassed 220 million copies in circulation worldwide. The anime, produced by ufotable, launched in April 2019 with the Tanjiro Kamado, Unwavering Resolve Arc. The theatrical trilogy Gekijouban Kimetsu no Yaiba: Mugen-jou Hen is currently in release, with Chapter 1 opening in Japanese cinemas on July 18, 2025.

Episode 12 — Story and Fan Reactions

⚠️ Spoilers follow.

Inosuke Makes His Entrance

The episode takes place inside the bizarre rotating mansion of the demon Kyogai, whose drum-beating causes the rooms to spin. Tanjiro also encounters a wild, boar-headed stranger who tramples the young girl Teruko — Hashibira Inosuke. After being thrown by Tanjiro, Inosuke declares, “That’s the first time a human has ever thrown me!” Fans reacted with a mix of amusement and exasperation: “Early Inosuke is genuinely awful,” alongside more forgiving takes like “Watching his growth from here is what makes it great.”

Zenitsu: From Coward to Lightning

Separated from Tanjiro, Zenitsu is left to escort Teruko’s brother Shoichi through the demon-infested mansion. Trembling with fear and sprinting away screaming “Don’t come near me~!”, he even begs Shoichi to leave him behind — only to be refused. Tearfully declaring “I have to do something,” Zenitsu then promptly passes out in front of the demon. Fans noted, “He’s unbearably cowardly, but he never actually abandons anyone — even from the very start.”

Then came the moment everyone was waiting for. As the demon attacked with its grotesque tongue, Shoichi cried out for Zenitsu to wake up. Eyes still closed, Zenitsu rose and whispered “Breath of Thunder, First Form — Thunderclap and Flash,” decapitating the demon in an instant.

The internet erupted: “HE’S HERE!! ZENITSU AWAKENS!!!” — “The gap between his two sides is insane” — “This is exactly why I love Zenitsu” — “He’s the ideal man — only useful when it truly counts.” When Zenitsu came back to his senses, he had no memory of what he had done and resumed panicking: “It’s suddenly dead?! What is going on?! I can’t take this anymore!” — sending fans into fits of laughter.

Tanjiro’s Legendary “Eldest Son” Line

Meanwhile, Tanjiro locates Kiyoshi, Teruko’s other brother, who possesses rare blood that had caused multiple demons to fight each other over who would get to eat him. Kiyoshi had survived by using a drum dropped by Kyogai to shift rooms and evade the demons. Tanjiro tenderly tends to Kiyoshi’s wounds and reassures both children before heading off to face Kyogai — despite his own body being badly injured.

In his internal monologue before the battle, Tanjiro lets out a silent cry of pain, then steels himself with the thought:

“I was able to endure it because I’m the eldest son. If I were the second son, I wouldn’t have been able to.”

The line became an instant viral moment. Fans called it “Tanjiro’s legendary quote” and praised voice actor Hanae Nobuhiko‘s passionate delivery for elevating it into a truly iconic scene. Others laughed: “Even eldest sons can’t normally endure that, though.” Either way, the moment resonated deeply as a window into Tanjiro’s stubborn, self-motivating spirit.

Special Cast Comment: Toki Shunichi (Voice of Kiyoshi)

The official Kimetsu no Yaiba account releases a special cast comment each week to mark the rerun. For Episode 12, Toki Shunichi, who voices Kiyoshi, shared his memories of the recording session: “Honestly, I didn’t expect to be given the chance to comment at all.” He recalled being deeply moved by the dedication of the main cast in the studio, saying he felt a responsibility not to break the world they had built, and gave everything he had to the role of Kiyoshi at that time. ufotable also shared an image of the original recording script cover for the episode.

Next Broadcast

The full-series rerun began on April 5, 2025, just ahead of the seventh anniversary of the original premiere. There will be no broadcast on June 28, 2026. Episode 13, “Something More Important Than Life,” will air on July 5, 2026, at 9:30 a.m.