Episode 1 of Kamen Rider MY-TH, broadcast in Japan on September 6, 2026, already establishes the series' basic rule: Sora Otosumi is a “Meister” serving the Mizuki family who transforms into the mouse-themed Rider to fight monsters called Fukashigi, while the Twelve Alliance awakens from a 100-year sleep to face the same threat. Both sides want to protect people, but they do not operate as allies — and the premiere makes clear that the mouse-versus-cat conflict predates the current protagonist.
This guide sticks to what the premiere episode and official pages published through September 9 support. Whenever the series has not yet explained an origin, motive, or full rule, that point is treated as an open mystery rather than a confirmed theory.
What episode 1 establishes about Sora and Yuna
Sora Otosumi works for the Mizuki family and looks after Yuna Mizuki, a first-year high-school student. Their relationship is not only domestic: Yuna investigates incidents connected to the Fukashigi, while Sora is the fighter who enters the field when a threat appears. The official episode guide shows them investigating a wave of human disappearances and predicting the likely location of another attack.
Sora's official character page adds an important detail about the word “Meister”: his family has served the Mizuki household for generations, and he is skilled at cooking, cleaning, repairs, and other household tasks. At the same time, he transforms into Kamen Rider MY-TH to protect Yuna. Yuna's profile confirms that she founded a school club devoted to researching Fukashigi incidents and supports the investigation.
The production also highlights a visual and functional distinction from the beginning: Sora wears the MY-TH Driver on his chest, while Riders tied to the Twelve Alliance wear their belts at the waist. That difference helps signal that MY-TH is not simply “another member” of the group.
What the Fukashigi are
The Fukashigi are the mysterious creatures threatening humans. Official introductory material describes them as monsters that attack and prey on people; in episode 1, their activity is connected to the “human disappearance incidents” investigated by Yuna and Sora.
The premiere, however, does not settle the origin of the Fukashigi. The official sources reviewed so far do not provide a full explanation of where they come from, why they are appearing now, or exactly how they connect to the transformation items and the Alliance's century-spanning history. For now, it is safer to separate narrative function from origin: they are the common threat, but their deeper nature remains open.
How the Twelve Alliance works
The Twelve Alliance (Jūnishi Dōmei) is an old organization created to protect people from the Fukashigi. According to the official introduction, its members entered a 100-year sleep in preparation for a future battle and have now awakened to resume their mission.
The decisive lore point in episode 1 is the group's own assumption: the Alliance believes that Fukashigi should only be defeatable by Riders from its Twelve system. That is why reports that someone outside its control is already eliminating monsters immediately become a problem. That outsider is Sora as MY-TH.
The “Twelve” refers to the animals of the East Asian zodiac, not the twelve signs of Western astrology. In an official production blog, TV Asahi recalls the traditional cycle of rat, ox, tiger, rabbit, and the other animals, while the cat is left out after being tricked by the rat. The series deliberately uses that folklore-based opposition as a symbolic foundation for its central conflict.
Why the mouse sits outside the current board
The official episode 1 guide reveals a lore detail that matters more than it first appears: there used to be a mouse within the Alliance, and that mouse defected. After that break, Kamuri Minetaka — the cat Rider known as Kamen Rider Maou — came to lead the group.
That means the clash between MY-TH and the Alliance does not exist only because Sora appeared in the present. There is an earlier history involving the mouse position and the cat's leadership. The lead actor's official post-premiere blog reinforces that reading by mentioning that the episode opens with a battle between a “previous MY-TH” and Maou.
What episode 1 still does not explain is why the mouse left the organization, whether Sora directly inherited that legacy, how the MY-TH Driver relates to the Alliance's equipment, and exactly what resulted from the battle in the past. Those remain open questions after the premiere.
Who Maou is — and why the cat leads the Twelve
Kamuri Minetaka is the current leader of the Twelve Alliance and transforms into Kamen Rider Maou, the cat Rider. His official profile describes him as someone who awakened from the 100-year sleep and resumed the fight against the Fukashigi. He is also presented as exceptionally strong among the Alliance's Riders.
The fact that a cat leads a group based on the traditional twelve animals is intentionally odd: the cat is not part of the classic cycle. The episode and official material use that anomaly to place Maou at the center of the conflict with the mouse. Even so, the premiere does not fully explain how the cat gained that institutional role or what happened to the mouse's original place.
What is confirmed and what remains open
| Point | Status after episode 1 |
|---|---|
| Sora is Kamen Rider MY-TH | Confirmed. He is the Mizuki family's Meister and fights to protect Yuna. |
| MY-TH has a mouse motif | Confirmed. The protagonist is officially presented as the mouse Rider. |
| Yuna takes part in the investigation | Confirmed. She researches Fukashigi incidents and works alongside Sora. |
| Fukashigi threaten humans | Confirmed. The episode links them to disappearances; official introductory material says they attack and prey on people. |
| The Twelve Alliance slept for 100 years | Confirmed. The group awakens in the present to resume the fight. |
| The Alliance expected only its Riders to defeat Fukashigi | Confirmed. An outside hunter immediately raises suspicion. |
| The mouse once belonged to the Alliance | Confirmed. The episode guide says a mouse defected in the past. |
| Why the mouse defected | Open. Episode 1 does not provide the full reason. |
| Origin of the Fukashigi | Open. The threat is defined, but its origin is not. |
| Exact relationship between the MY-TH Driver and Alliance belts | Open. The wearing difference is confirmed; the systems' lineage is not yet explained. |
Lore terms worth remembering
- Meister: Sora's role in service to the Mizuki family; his lineage has served the household for generations.
- Fukashigi: mysterious creatures connected to attacks and disappearances.
- Twelve Alliance: a century-old organization tied to the East Asian zodiac animals and the hunt for Fukashigi.
- MY-TH: Sora's Rider form, associated with the mouse and using a chest-mounted driver.
- Maou: the cat Rider and current leader of the Alliance.
What episode 1 wants you to carry forward
Rather than simply introducing one hero and one rival group, the premiere sets up two lines of defense against the same enemy. Sora and Yuna operate independently; the Alliance returns with rules, memories, and a hierarchy that predate the protagonist. Their collision happens because both hunt Fukashigi, but the Alliance sees MY-TH's existence as a breach in an order it considers its own.
So the central question after the first episode is not only “who will defeat the next monster?” It is who has the right to the mouse legacy, why that legacy was broken, and what Maou's past has to do with the present MY-TH. Episode 1 confirms that this past exists, but keeps its causes hidden — exactly the kind of mystery the series appears designed to resolve through its serialized story.
