L'Arc Berg, also called L'Arc Berg Sickle or The Scythe Hero, hails from a world endangered by the Waves of Catastrophe, a world shared with Glass and Therese Alexandrite. As the Vassal Hero wielding the Vassal Scythe, his role differs from the Cardinal Heroes of Naofumi Iwatani's world. He rules his homeland as king, ascending to the throne after his father's death. Despite his royal position, he values personal freedom and dislikes authority's constraints, though his effective leadership earns his subjects' respect. He possesses spiked red hair, red eyes, and a muscular physique, with a scythe tattoo visible on his upper arm. His personality is generally carefree, laid-back, and charismatic. He approaches problems with a relaxed attitude, showing playful, almost childish excitement in new situations like a ship ride. A strong warrior spirit drives him; he relishes fair fights and challenging battles. He maintains high moral standards, expressing reluctance and remorse when his mission forces him to harm those he judges as good people. He quickly and accurately assesses character. He often addresses younger individuals as "Kiddo" and develops a brotherly rapport with Naofumi Iwatani after their initial conflict. As the Scythe Hero, he demonstrates exceptional combat prowess, wielding his Vassal weapon with masterful speed, strength, technique, and intuition, including wind-based attacks. His battle effectiveness increases significantly when supported by Therese Alexandrite's jewel magic. Trained for years in his native world, he is a formidable opponent capable of challenging multiple adversaries. Introduced during the Cal Mira Island arc, L'Arc and Therese approach Naofumi under false pretenses of friendship aboard a ship. After level-grinding with Naofumi's party, his true mission surfaces during the Wave event: kill Naofumi's world's Cardinal Heroes to prevent his own world's destruction during the Waves' interdimensional merging. He specifically targets Naofumi, conflicted by the necessity of killing someone contradicting the Shield Hero's negative rumors, openly dismissing the other three Cardinal Heroes as weak. Following the rescue of Kizuna Kazayama, the Hunting Hero from his world, his relationship with Naofumi shifts from antagonism to alliance. He abandons his mission to eliminate the Cardinal Heroes, becoming a trusted ally and protagonist who cooperates with Naofumi's group to find solutions potentially saving both worlds from annihilation.