Hexagon, formally Rokkaku Tsumadaru, serves as an antagonist within the Earth Wolves faction. He attends Hinomori Academy Middle School alongside fellow Earth Wolves members and the Heart Princesses. His physical appearance features blue hair cut in a bob and glasses, creating a distinctive look. Hexagon exhibits a nerdy personality, functioning as the intellectual strategist for the Earth Wolves. Despite opposing the Heart Princesses, he develops unrequited romantic feelings for Blue Princess Ami Gidou, introducing personal conflict into their factional rivalry.

Hexagon summons Sinbeasts called Zaiju to attack Hinomori city, furthering the Earth Wolves' goal of seizing Heart Spheres from the Princesses and Moon Cats. His actions and interactions primarily unfold within the school environment and during direct confrontations with the protagonists.