Helck is a fantasy anime series that blends action, comedy, and drama, set in a world where humans and demons are locked in a prolonged war. The story begins in the aftermath of the Demon Lord's defeat, as the demon realm holds a tournament to select a new leader. Among the participants is Helck, a human hero who claims to hate humanity and wishes to destroy it. His overwhelming strength and cheerful demeanor make him an enigmatic figure, drawing suspicion from the demon populace, particularly Vermilio, a high-ranking demon officer tasked with overseeing the tournament.

As the tournament progresses, Helck's true motives and past are gradually revealed. Despite his outward hatred for humanity, Helck is revealed to be a compassionate and selfless individual, driven by a deep sense of justice and a desire to protect others. His cheerful personality masks the pain of losing his brother, a tragedy that shaped his resolve to fight against the true threat to both humans and demons: an ancient, malevolent force known as the "Otherworldly King." This entity seeks to annihilate all life, forcing humans and demons to confront their shared enemy.

Vermilio, initially distrustful of Helck, grows to understand his character and motivations. Her perspective shifts as she uncovers the truth about the Otherworldly King and the impending catastrophe. Alongside Helck, she becomes a key figure in uniting the demon realm against this existential threat. The narrative explores themes of unity, sacrifice, and the complexities of morality, as characters from both sides of the human-demon conflict are forced to reevaluate their prejudices and alliances.

The series balances its darker, more serious moments with lighthearted humor, often derived from Helck's eccentric personality and the absurd situations he finds himself in. Supporting characters, such as the demon warrior Azudora and the enigmatic mage Anne, add depth to the story, each contributing to the overarching plot in meaningful ways. The interplay between Helck's unwavering optimism and the grim realities of war creates a compelling dynamic, driving the narrative forward as the stakes escalate.

Helck's journey is one of redemption and resilience, as he confronts both external threats and internal struggles. The series culminates in a climactic battle against the Otherworldly King, testing the limits of Helck's strength and resolve. Through its exploration of camaraderie, loss, and the fight for survival, Helck delivers a narrative that is both engaging and emotionally resonant, appealing to fans of fantasy and action genres.