Light is a young human boy with black hair and yellow eyes. He intentionally wears a magical item called the Bracelet of Youth, which he obtained from his own Gift, to keep his appearance fixed at around twelve years old. He does this as a self-imposed reminder of the despair, sorrow, and rage he felt at the moment he was betrayed. Light grew up in a world where humans are widely regarded as the weakest race. Seeking to prove his own worth and the value of humanity, he joined a multiracial adventuring party known as the Concord of the Tribes. During a mission into the most dangerous dungeon in the world, the Abyss, his comrades turned on him and abandoned him to die in its deepest reaches. Left for dead and on the brink of death, Light's innate magical skill, the Unlimited Gacha, finally awakened to its true potential. In the high magical density of the Abyss, what had previously been considered a useless power capable of producing only junk items became overwhelming. It allowed Light to summon cards of Super Ultra Rare rarity, each bringing forth a Level 9999 ally. His very first summon under these conditions was Mei, a maid warrior of immense power who saved his life and became his most loyal companion and trainer.

Driven by the trauma of the betrayal, Light vowed to take revenge on his former party members and to uncover the truth behind why they betrayed him. His motivations extend beyond personal vengeance, as he also seeks to prove the value of humans and to challenge the systemic oppression his race faces in the world. His single-minded focus on revenge initially defines much of his personality, hardening him and stripping away the innocence he once had. However, after reuniting with his younger sister, Yume, glimpses of his former, more vulnerable self begin to resurface. His love for his family is profound, and he is willing to do anything to protect and reunite with the relatives he has left.

In terms of his role in the story, Light is the central protagonist who transforms from a betrayed victim into a powerful overlord. Over the span of roughly three years, he carves out a hidden kingdom within the Abyss, amassing an army of Level 9999 summoned warriors who swear absolute loyalty to him. His key relationships are primarily with these summoned beings. Mei serves as his most trusted confidant, trainer, and enforcer, while other summoned allies such as the knight Nazuna, the brawler Jack, and the catgirl Aoyuki form the core of his military force. As he grows in power, Light plans to ascend to the surface and systematically confront each of his betrayers.

Light's primary ability is the Unlimited Gacha, which functions as a summoning system that draws cards to invoke allies and items. In the Abyss, its full potential is unlocked, enabling him to consistently summon beings of the highest level and rarity. Through this power, he also obtains magical items, such as the Bracelet of Youth, and commands an expanding army of max-level servants. His character development traces a classic power fantasy arc, rising from a powerless and discarded boy into the sovereign of the Abyss, with his journey fueled by a desire for revenge and a broader fight against racial discrimination.