"Ikenie no Susume" is a dark fantasy manga that explores themes of sacrifice, survival, and the consequences of human desperation. The story is set in a dystopian world where humanity faces extinction due to the emergence of monstrous creatures known as "Shinju." These beings are invulnerable to conventional weapons, and their presence has driven society to the brink of collapse. In response, a mysterious organization known as the "Order of the Holy Grail" emerges, offering salvation to humanity through a grim ritual: the selection of "sacrificial offerings" who must willingly give their lives to summon powerful entities called "Guardians" to combat the Shinju.

The protagonist, a young man named Shougo Mikadono, becomes entangled in this brutal system when his sister, Ayaka, is chosen as a sacrificial offering. Determined to save her, Shougo volunteers to take her place, entering a deadly game where he must fight alongside other offerings to survive. The Guardians, summoned through the sacrifices, are bound to their human partners and possess immense power, but their use comes at a steep cost: the gradual erosion of the human's life force.

As Shougo navigates this perilous world, he forms alliances with other offerings, each driven by their own motivations and haunted by their pasts. Among them is Rikka Hoshigami, a stoic and skilled fighter who becomes a key ally, and Yuuto Kiba, a rival whose methods and ideology clash with Shougo's. The narrative delves into the psychological toll of the sacrifices, as the characters grapple with the moral implications of their actions and the inevitability of their fates.

The plot unfolds through a series of intense battles against the Shinju, interspersed with moments of introspection and character development. The Order of the Holy Grail, while presenting itself as humanity's last hope, harbors dark secrets and ulterior motives, adding layers of intrigue to the story. As Shougo and his companions uncover the truth behind the Shinju and the Guardians, they are forced to confront the harsh realities of their world and the sacrifices required to change it.

"Ikenie no Susume" combines action-packed sequences with a thought-provoking exploration of human resilience and the cost of survival. The manga's narrative is driven by its complex characters, whose struggles and relationships are central to the unfolding drama. The story's dark tone and morally ambiguous themes create a compelling and immersive experience, making it a notable entry in the dark fantasy genre.