The main hero of the story. Rei is obsessed with being number one. He doesn't remember his past but doesn't seem to care very much. He is an ultimate-user, who has an unusual ultimate symbol on his heart. He eventually gains ultimate cards of all six colors, and a separate form for each.
All-Loving Hero: Anyone is a "serious friend" to him, even those who have really done nothing to deserve the title. As more proof that he's one of these, Ultimates find him worthy left-and-right.
Amnesiac Hero: He woke up with two Ultimates, and didn't remember anything before that.
"The Number One Star Burns Bright Red! There's no one Stronger than Me." (Burning), "The Number One Star shines white! Sound the song of victory!" (Silver), "A favorable wind for sailing! It's a Tailwind!" (Hurricane), "Well then, let's meet again in a wonderful hell." (Flash), "No enemy can block the path to my boundless future!" (Azure), "That was Zero the Glint!" (Glint)
Curb-Stomp Battle: He tends to have these with the Triumvirate, with Rei of course being the one doing the stomping.
Elemental Hair: Each of his forms comes with an appropriate hair-color change.
Large Ham: All of his alternate forms. Just look at some of the catchphrases. Yuichi Nakamura does an amazing job overracting. Glint particularly stands out, for treating his battle like a concert, complete with an imaginary audience he encourages to cheer for him.
Gasshole: And how, Farting is one of Mugen's most defining Characteristic. Usually he farts at Triumvirate or anyone he's really mad at or don't like.Sometimes he even use his farts to attack his opponents in game. In the earlier episodes Mugen would often let out a huge fart when he changes from a red spirit to a white one.
Kiriga is a powerful member of the guild, who often does tasks for Miroku. Like Rei, he has a dragon companion. He also has a missing past, and an ultimate symbol on his heart. Eventually, he leaves the guild and finds his memories on his own.
The Dragon: He serves as this for Miroku at the start of the series.
Forced Into Evil: It's later revealed that he was following Miroku because Miroku had his memories which he wanted back.
Heel-Face Turn: He eventually leaves the guild, and decides to fight against the invaders from the other dimension.
Undying Loyalty: To Kiriga. It's obvious he doesn't think highly of the guild, but he sticks around because of Kiriga. And you can see how much it pains him having to watch Kiriga get tested by Ultimate-Grand-Woden
Miroku is the guild's leader. He keeps his face hidden under a visor. He tends to act very sadistic. Miroku's ultimate objective is for all of space to be his. To carry this out, he summons users of the Reverse 12 Zodiac Braves from an alternate dimension, to combat the Ultimate-users.
Evil Laugh: He starts doing this quite a bit later into the series.
Expy: He has a lot in common with Zazie in Brave. They're both masked white-haired villains with an alter ego, not to mention massive trolls. Both try to summon an Ophiuchus card and the process involves sacrificing their own supposed allies. Miroku even imitates Zazie's battle style.
Kick the Dog: He regular tortures the Triumvirate, sometimes seemingly for no real reason. He takes this cruelty a step further after stripping Hansoro of his memory, blowing up his ship, and leaving him to die in the snow.
You Have Failed Me: It's obvious he does not have much tolerance for failure. He finds inventive ways to torment the Triumvirate whenever they mess up and when Hansoro betrays him... it gets much worse.
The Galaxy Triumvirate (Tsuruhashi the Waking, Hashibuto the Angry, Watari the Flowing)
The Galaxy Triumvirate is a team of guild members. They want to steal the space compass for Miroku, but constantly fail. All three of them were former performers. Tsuruhashi is known for rapping, and uses red. Hashibuto is a feminine crossdresser, who uses purple. Watari is a Magical Star fanboy, who uses white.
Pet the Dog: There is a whole episode devoted to Watari (and the others by extension) helping Magical get a break from her work by pretending to kidnap her. Though it backfires for them, Magical was still very thankful.
Well-Intentioned Extremist: He is a strong supporter of the guild because he believes that if everyone follows their code, it will put an end to conflicts over cards. Although he was disturbed by Miroku's true ambitions, note that one thing Hansoro was in support of was the Seven Galaxy Generals, who enforeced the guilds law by going around oppressing people.
The leader of the Seven Galaxy Generals. He steals one of the faucets from Planet Faucet, to make better pickled vegetables. He is also an ultimate user. After losing to Rei, he reforms himself, and goes off to raise vegetables.
Ineffectual Sympathetic Villain: Not as much as the Triumvirate, but after seeing him lose to both Kiriga and Eris, and then get easily eliminated by Magical Star in the Justice Cup, only to be mocked by both Denebola and Miroku, it's hard not to feel sorry for him.
Villain Decay: Big time,when from being a dangerous new enemy that was able to easily defeat both Kiriga and Eris. to a complete loser overnight.and now he is no longer take seriously and is now easily defeated by Kiriga ,Eris ,and Magical Star of all people.
Eris is the leader of a crew of just pirates, who oppose evil. She is an ultimate-user who has a yellow deck. She later finds a dragon partner in Chocola, and gets chosen by one of he Tri-Dragon Deities, allowing her to gain an ultimate symbol like Rei and Kiriga's.
Action Girl: She eventually gets chosen by a Tri-Dragon Deity, and gains an ultimate symbol just like Rei and Kiriga
Amazon Brigade: She has an all girl crew. Also, her deck, which is composed of female spirits/Ultimates including her Tri-Dragon Deity.
Eris' dragon companion. She thinks of herself as a lady. Very excitable, she will usually repeat all her words.
Batman Can Breathein Space: She was able to talk, take a deep breath and blow away a nebula. All while being in the vacuum of space
Balloon Belly: She had this when she inflated herself when taking a deep breath before blowing a way a nebula.
Beauty Is Never Tarnished: Played straight, She is the only one of the three chibi dragons that doesn't use fartillery.Probably because she's the only out of the three that's a girl or because she wants to be seen as a lady and as we all know real ladies don't do fart jokes.