Kaiten Mutenmaru is a Collectible Card Game and webcomic series by the restaurant chain Kura Sushi beginning in December 2007. It consists of fourteen parts across two seasons in both media, plus one final part in the webcomic.
Mutenmaru is a little samurai who lives with his grandmother alongside his childhood friends, Kurara and Kurakichi, in Bikkura Village. They lead a peaceful life until Tsubukante and his four minions show up to conquer the world with additives, leading Mutenmaru to follow in his murdered father's footsteps and protect the taste of sincerity from the villains. In Season 2, the Abominable Crystal — initially known as disium in the game and the original serialization of the webcomic — poses a threat to the world by turning people into monsters. Spreading it to cause chaos is Sick Valachlorophenol, a self-styled gentleman corrupted by the crystal himself. To combat the new forces of evil, Mutenmaru is joined by new companions consisting of:
- Kura Shishi no Mikoto: A fiery lion spirit sealed in one of the cards belonging to Mutenmaru's father. He becomes Mutenmaru's partner when the boy finds his card.
- Umimi Sheela: The princess of the mermaids who's dreamed of adventuring because of her lifelong confinement at the hands of her well-intentioned father, King Ocean. Her singing has magical powers, including the ability to heal injuries.
- Tear Crown: A female water spirit sealed in one of the cards belonging to Mutenmaru's father. She becomes Umimi's partner after the mermaid's song awakens her.
- Siam Merluza: A simple-minded Cat Girl who loves freedom and fighting the strong. She's the leader of the Cat Thieves.
- Shinobu Kajika: An orphan turned aspiring hero themed after ninja.
- Grinbear Salmon: A magical young bear capable of human speech. His personality changes depending on the outfit.
- Leaf Cloud: A leafy spirit bird sealed in one of the cards belonging to Mutenmaru's father. She appears out of her card when Grinbear struggles to save his mother from the corrupting influence of the Abominable Crystal.
- Tetsujin Granchio: A robot chef working at the restaurant Corale in the town of Europia. Once a soldier called Tetsujin Unit 1, he's grown beyond his programming thanks to a blind old woman who mistook him for her son Granchio and taught him humanity.
The webcomic ran on the official website of the franchise until October 26, 2015, with a total of 166 chapters. Season 2 was also serialized in Manga Goccha and pixiv Comic, with extra illustrations drawn specifically for the former magazine.
Kura Sushi published a motion comic adaptation of the first chapter in Season 2 on YouTube in 2014. Micro Magazine published the first two parts of Season 2 in four books in the same year and 2015 respectively.
On every April Fools' Day from 2014 until 2016, characters would take over the official Twitter account and answer questions from fans. Kura Sushi published extra material taking place after the epilogue from November 11, 2015, to May 13, 2016, all of which you can find here.
A general introduction to the series can be found here.
As there is no official English translation, the terms used here may not be always correct.
Kaiten Mutenmaru provides examples of:
- All There in the Manual: Supplementary information, including the worldbuilding and the names and personalities of some characters, comes from trading cards, tweets from the official accounts, extra illustrations in the Manga Goccha serialization, and the books.
- Art Evolution: Mutenmaru starts out with an oval head, thick lines, and a reflected light on his bald head. He gets a rounder head in The Training and loses the reflected light in Season 2, which uses thinner lines than before overall.
- Art-Style Dissonance: The cutesy art style of the series belies at least one backstory featuring social inequality, Star-Crossed Lovers, civil war, and the Death of a Child.
- The Corruption: The Abominable Crystal is a mysterious material that grants the infected superhuman powers at the expense of corrupting them into monsters. The transformation in mind and body can be gradual, as implied by Orcus, Crocell, Pain and Yamai.
- Phenotype Stereotype: Shinobu Kajika, Shinuka To'omotta, Crocell Xylel, Mackerel, Anchor Web, Sister Meer, and Anchor Sam have blonde hair, along with blue eyes in the cases of the last five, to emphasize their American origins.
- Power Crystal: The Abominable Crystal is a powerful but corrupting material that turns people into monsters.
- Purple Is Powerful: The Abominable Crystal is colored purple to emphasize its ability to grants the infected superhuman powers at the expense of turning them into monsters.
- Journey to the Center of the Mind: Leaf Cloud sends Grinbear to his mother's mind, allowing him to purify her of the Abominable Crystal.
- Journey to the Center of the Mind: Tear Crown enters Sissela's mind to bring Umimi back from the corrupting influence of the Abominable Crystal.
- Children Are Innocent: As little children, Sick Solitude and Anne Bran were the only good people in the town of Throne from the start. Anne was also the only commoner to oppose violence and to value Sick as a person rather than judge him solely based on the decadence and tyranny of his parents.
- Family Extermination: The rebels decided to exterminate the Solitude family, not caring that Sick was a child with no connection to the tyranny of Pain and Yamai over the town. Although they apparently succeeded in killing Pain and Yamai, Sick survived with the help of Anne and turned into a monster seeking revenge for their atrocities.
- Pensieve Flashback: The crystals in the Ruins of Time draw Tetsujin into Astar's encounter with Sick, whose horrific past the rest of Mutenmaru's group relive.
- Puppy Love: Sick Solitude and Anne Bran were in love with each other as little children.
- The Revolution Will Not Be Civilized: The poor mob burned and looted the house of their aristocratic oppressors, Pain and Yamai Solitude, but that's not the most horrible part about their rebellion — they also targeted Sick as a child solely for being the son of the Solitudes and killed a commoner girl his age in a blind rage for trying to stop them.
- Tyrannicide: The rebels in Sick's backstory not only planned to kill the Solitude family and burn their house but also killed their young peer in a blind rage. This, along with their triumphant return, implies that they succeeded in killing Pain and Yamai for their tyranny over the town of Throne, leaving Sick an orphan and the only survivor of the family.
- Would Hit a Girl:
- Sick beat Anne when his butler caught them on a date. He's apologetic about having to hide their relationship that way, though.
- One of the poverty-ridden rebels thrust Anne away when they suspected her of being a spy for Sick, the innocent son of their aristocratic oppressors. They killed her in a blind rage for trying to stop them afterward, with horrific consequences.
- Would Hurt a Child: The poverty-ridden rebels targeted Sick as a child solely for being the son of their aristocratic oppressors, with heavy implications that they would also have killed him if Anne, Sick's girlfriend his age whom one of them thrust away beforehand, hadn't stepped in and been killed in a blind rage.
- You Monster!: During the Pensieve Flashback to Sick's past, Mutenmaru fearfully calls the poverty-stricken rebels monsters for being motivated by hate after one of them thrust little Anne away in the belief that she's a spy for the aristocrats. Mutenmaru often expresses compassion for the actual monsters he fights, making his reaction to the humans stand out.
- Young Love Versus Old Hate: The young love between Sick Solitude and Anne Bran was doomed in the rebellion by the hateful commoners against their aristocratic oppressors, Pain and Yamai Solitude. It's heavily implied that only the bearded man with cat ears was wise enough to realize the atrocities of his peers after the murder of Anne.
- Reincarnation: Jagan, Astar, and Trishna reincarnate in the epilogue and extra material. Sister Meer takes Jagan in at the request of Eryth and Ritol while Astar and Trishna work alongside Tetsujin in Corale.