Maruss and Rembrant form a duo that quickly sets their sights on Tia and Megumi early in the Mamodo battles. Their element is metal. Maruss used to be Tia's best friend in the Mamodo World, showing care and protection towards her, unlike his bullying behavior towards Zatch. However, once they entered the human world, his mindset shifted, believing that true friendship was impossible due to the competitive nature of the fights and that one must oppose others to become king. Rembrant, on the other hand, is a power-hungry, blabbering fool who thinks he can dominate the world with his Mamodo, Maruss.
When Tia and Maruss reunite in the human world for the first time, he betrays her and launches an attack, sending her into the ocean. After Tia survives and finds refuge with Megumi, Maruss and Rembrant repeatedly pursue and assault them, driven by Megumi's fame as an idol. During one of Megumi's concerts, while they were attacking Tia, Zatch steps in to defend her, confronting Maruss until both sides' bookkeepers join the fray. In the end, it is Zatch, the former "weakling" whom neither Tia nor Maruss took seriously, who triumphs over the arrogant Mamodo, tearing Maruss's shirt in the process, and compels Tia to reconsider her views on friendship amidst the chaos of battle.
