|Appears In:||Yu-Gi-Oh! GSTART|
|Voice Actor||Shannon Chan-Kent as Beatrice "Trixie" Sting (Slugterra)|
Cleo has amber hair in two side ponytails that come down to her biceps, slightly tanned skin (stated as midtone between Kohaku and Plata), and big blue eyes. Her primary outfit is a sailor fuku school uniform that is predominantly black, but has gold trim.
Cleo initially appears as a stereotypical uptight and prideful Class Rep, calling Kohaku's group "ragtag" and stating that they need some class, also apparently not taking teasing well. However, she is humble and a woman of her word, deciding against taking her anger out on an innocent and upholding a stiff wager after a loss. Later appearances, however, show her mellowed out and comfortable hanging out with Kohaku's group, also exhibiting some more girly-girl traits such as a fondness for jewelry. She also tends to exhibit some devious tendencies, such as acquiring a fake marriage document to intimidate Kohaku.
Cleo Hamun is first introduced as the Class President of Kohaku's homeroom in Delta High, trying to pass a movement to initiate school uniforms as mandatory (which Delta High doesn't do). According to a comment by Plata, Cleo has an Egyptian ancestry. She quickly chases after Kohaku to try and beat him up after he makes an off-handed comment, but doesn't find him until he is in Delta High's Central Area, about to teach Kuran Hiwatari how to Composition Summon. Initially about to take her anger out of Kuran, she decides against it and instead intimidates Kohaku with a document claiming that he is legally married to her, stating she'll show everyone it if he doesn't help. However, Kohaku places the campaign as a Duel wager. Confident, Cleo ups the stakes and places the state of the marriage certificate on the line, but it backfires and she loses. Upholding her word, Cleo rips up the certificate yet also reveals that it was fake, shocking them. The next day, Cleo is teased during her school-opening speech by Yoru falling asleep on purpose, but her anger is defused by Kohaku, who says (honestly) that none of them mean any disrespect: They're just having a little fun. Cleo believes him, removing her angst.
She later appeared during Delta High's Self-Art Plaza, now friendly to Kohaku's group. Like them, she is highly put off by Kaneko Batosei's haughty attitude. Upon seeing Plata's makeshift jewelry, she is awed, agreeing with a comment that she has a knack for flair.
- According to Taylor Gorrell, Cleo's initial character as a stereotypical "Class Rep" character was going to stick, but Taylor felt that he wasn't able to make that character very convincing, so Cleo was subsequently softened up in Chapter 4.
Cleo plays a Hieroglyph (AKA Tributing strategies for her effects. According to Kohaku, Cleo is one of the few people to still use Xyz Monsters (though this could've been a lie, since Kohaku didn't respect Xyz Monsters at that point).) Deck, using mass