Maru was born shortly before the Calamity, though his true identity remains uncertain. His mother, Tokio, gave birth to a single child, but the infant was later cloned by Sakota. During the raid on Heaven, the two identical children were mixed together. Unable to distinguish which was the original, Teruhiko marked a circle on the sole of one child’s foot. The marked child would later become known as Maru, while the unmarked child remained with Tokio. Maru himself was taken outside the Takahara Academy during the chaos of the Calamity and ended up in the care of Aoshima.

Unaware of his origins, Maru grew up without knowledge of his parents and spent his early years migrating between different groups of survivors. His life changed when he encountered Mikura, who taught him self-defense and introduced him to the technique known as the “Maru-Touch.”

As Mikura’s health began to fail, she resolved to entrust Maru’s safety and future to someone else. She hired Kiruko, an odd-job worker and bodyguard, to escort Maru to the place known as “Heaven.” Before she could share the full details of her mission, Mikura collapsed and died, leaving Maru and Kiruko to embark on the journey together.

Maru is depicted as a boy in his mid-teens with a lean build and youthful features. He has spiky, light gray hair and matching gray eyes, giving him a distinctive look compared to many of the survivors in the ruined world. His appearance is often described as androgynous, to the point that he is frequently mistaken for a girl.

His typical attire reflects both practicality and individuality. He wears a black hooded dungaree with sleeves, which bears the phrase “We are neither machines nor game pieces” across the back, a statement that underscores his journey and identity. Beneath this, he wears a yellow undershirt, along with black mid-top trainers that feature red soles. For travel, he carries a durable green army-style camping bag, which holds supplies necessary for his survival on the road.

Maru’s overall appearance is simple yet memorable, balancing the ruggedness of a wanderer with a youthful charm. Kiruko herself has commented on his good looks, reinforcing the impression that his delicate features stand out even in a harsh, post-apocalyptic environment.

Maru is portrayed as a complex individual who balances resilience with vulnerability. Despite his youth, he demonstrates strong survival instincts and a pragmatic outlook shaped by years of hardship in a collapsing world. His determination to push forward is a defining trait, particularly in his mission to reach “Heaven,” though he often grapples with uncertainty about his origins and role in the larger mysteries surrounding him.

Though intelligent and perceptive, Maru’s sharpness sometimes isolates him, as he tends to overanalyze situations and struggles to fully trust others. Nevertheless, his bond with Kiruko softens these tendencies, allowing him to show a more playful and lighthearted side. Around her, he is comfortable joking, sharing personal thoughts, and displaying the insecurities he usually hides.

Maru is also characterized by his straightforwardness and honesty. He does not shy away from expressing his feelings, as seen when he openly admits his attraction to Kiruko, even though she cannot reciprocate. This blend of determination, self-awareness, and emotional openness makes him a grounded yet relatable presence within the story, embodying both the strength to survive and the longing for genuine human connection.

Kiruko
Maru develops romantic feelings for Kiruko over the course of their journey. Despite knowing the truth about her past and dual identity, he openly admits that he still wishes to be with her, stating that he has never met a girl with whom he got along so well. Nevertheless, Maru most often addresses her as “sis,” reflecting both his affection and the sibling-like bond that underpins their companionship.

Michika Takezuka
Maru’s first encounter with Michika Takezuka quickly escalated into a fight, marking the first time he had ever experienced defeat in combat. The following day, the two clashed again inside a warehouse, exchanging blows until they both collapsed from exhaustion. In the aftermath, each claimed the other had won the fight. Maru grew intrigued by Takezuka, particularly because she used the term “Hiruko” to describe the creatures he and Kiruko knew as Man-Eaters.

Hiruko Physiology
Maru was born with a Hiruko core, granting him abilities that surpass ordinary humans.

Maru-Touch
Through direct hand contact, Maru can invade a Hiruko’s body in search of its core. This ability enables him to almost instantly kill a man-eater. However, when using this power, his consciousness is transferred into the Hiruko’s body, leaving him in a state of extreme vulnerability.

Enhanced Combat Skills
Maru possesses physical strength and speed far beyond human limits. He can move faster than the eye can track, render opponents unconscious with a single strike, and withstand high falls without injury. He demonstrates advanced martial arts proficiency, even managing to tie with Michika in hand-to-hand combat.

Hiru-Sense
Maru can detect the presence of organisms containing a Hiruko core in his vicinity.

Regeneration
His body displays advanced healing capabilities. He recovered from a swollen, bleeding comatose state in just three days and has shown the ability to regrow lost teeth.

Kiru-Beam
Kiruko carries a specialized energy weapon known as the Kiru-Beam. The gun is capable of disintegrating nearby objects with concentrated blasts of energy. However, its use is limited, as it can only be fired four times consecutively before requiring a recharge. Although somewhat unreliable, the Kiru-Beam has repeatedly proven invaluable, saving both Kiruko and Maru during life-threatening encounters.

Flashlight
Kiruko also uses a portable Nanogrid lamp produced by Biolite. This flashlight is a practical survival tool, aiding her and Maru in navigating dark or unsafe environments during their travels.