- "From now on, except my allies, all of you are 'Witches'!"
—Aguni in the manga Chapter 21
Morizono Aguni is a character first appears in the Beach arc and the leader of the "martial sect" of the Beach residents.
Aguni's father was a sore loser and problem drinker. He constantly abused his son and wife after returning home carrying another drink. To draw the attention away from his mother, the frightened Aguni retorted his abusive father but his mother did not stay long in their home. Aguni also ran away from his father when he was 12 years old.
Aguni and Takeru Danma (Boshiya) had been sworn friends when they were 16 years old. Both messed with bunch of street thugs but easily crushed them with just 2 men. Turning 17 years old, Aguni probably wanted to beat his father for revenge, only learned that he died of acute alcohol poisoning half year after Aguni's leave.
Borderland: First stageEdit
After winning some games, Aguni helps Boshiya to establish the utopia by keeping the trouble makers under control so they do not disturb the equilibrium of the Beach society, a role he agrees to assume until Boshiya murders the residents for hiding the cards which should be handed over for the society. Disappointed by Boshiya's heightened spirit of brainwashing the residents with the false method of departing the Borderland, Aguni calls out Boshiya right after the latter has just been returning from game and bids farewell. Boshiya points his gun on the back of Aguni but he quickly shoots back and kills him, only learns that Boshiya's gun is not loaded. He finally understands that Boshiya has been concealing his fear of being unable to escape the Borderland. Boshiya would rather die in his best friend's hand than by anything else.
Aguni is devastated. When the Ten of Hearts (Witch Hunt) begins in the next evening, he orders his underlings to murder anyone not in their sect, making them believe that they are merely doing what the game requires them: Throw the "Witch" into the bonfire before timeout. The fact is, Aguni wants to lead everyone to game over so all Beach residents, including himself, are buried with the false hope spread by Boshiya. Even hearing Ryōhei Arisu's revelation of his true motives and reasoning, Aguni still claims himself to be the Witch and delays everyone else to proceed. His rampage is only distracted when Asahi attempts to reveal her true identity as the dealer which activates the blazing laser of execution. The game has been cleared, but the Beach resort is destroyed in fire set by Niragi. Aguni hides himself from the crowd, probably out of guilt.
Borderland: Second stageEdit
Aguni sets up his lone garrison in a forest away from the city center awaiting Isao Shīrabi (King of Spades)'s approach. He wants to atone his sin via a meaningful death. After saving Hayato Dōdō from Shīrabi, he does not hesitate to point out how cowardly and useless Dōdō is for surviving all along over the sacrifices of others, but decides to train him in the vague hope of outnumbering Shīrabi. Dōdō still proves not much of a helping hand when he is commanded to aim and shoot Shīrabi in a crossfire. Aguni lets Dōdō run away and rushes himself towards Shīrabi, the latter is impressed by Aguni's resolve and retreats. Sometime later, Aguni again saves Dōdō from the torrent and meets Akane Heiya after the latter two have destroyed Shīrabi GPS device. Aguni is hugged by Dōdō for feeling sorry and grateful that they are still alive. Aguni is also asked by Heiya if he would be interested in her sexually, to which Aguni instantly rejects her. Besides the possibility of being gay, Aguni has been prepared to sacrifice his life anytime soon, hence his rejection to getting involved with other people. But when the three are eating together in a grocery store, after hearing Dōdō's comment that they are like a family even though their ages do not line up, Aguni secretly admits to Boshiya's shadow created by himself that he will assume the duty of a father to protect his own son.
Just when Dōdō and Heiya are asleep, Aguni quietly leaves to somewhere to set up a leaking fuel trap for Shīrabi which would kill both of them, but Dōdō quickly approaches Aguni, refusing someone to die for his sake. Dōdō tricks Aguni to escape from Shīrabi via a wire received from Heiya and shoots at Shīrabi, but all shots are voided by the bulletproof vest. Dōdō loses his balance after barely hit by Shīrabi's shots and falls into the mud flow below. Shīrabi then uses the same wire to approach Aguni. Aguni, in deep despair over Dōdō's apparent death, rushes towards Shīrabi, taking numerous shots before closing the distance and punches Shīrabi's head hard, this time Aguni successfully disables Shīrabi. Before dying, Shīrabi mutters his regret for not being able to save his former commrade Apache, Aguni assumes this commrade and forgives Shīrabi. This also gives Aguni salvation for his regret over Boshiya's death. Rejoicing their victory and Dōdō's survival, the announcement declares only Aguni's visa is extended instead of anyone else, this leaves Dōdō in deep peril as his visa will expire that day. Luckily the last game, Queen of Hearts, is cleared by Arisu and Usagi in the same day. Aguni like his allies chooses to return to the original world, he is last seen unconsciously lying in the hospital bed, watched over by Dōdō and Heiya who preserve no memory of their time in the Borderland.
- Aguni's alias coincides with the Japanese rendition of the Vedic supreme divinity of fire, Agni.