Kyuusaku Yumeno, often referred to by the nickname Q, is a thirteen-year-old member of the Port Mafia in Bungo Stray Dogs. Their appearance is strikingly androgynous, with short two-toned hair that is white on the left side and black on the right. Their eyes are similarly mismatched: the right pupil is a solid yellow star, while the left is a yellow ring with a dark blue center. Yumeno typically wears a small hat, a white shirt with suspenders, a black coat, a scarf, beige shorts with thin red stripes, high white socks, and brown shoes. They carry a doll in a red sling bag, which is integral to their ability.

Yumeno first appears in the second season of the anime. They joined the Port Mafia shortly after Osamu Dazai’s own recruitment. Initially, Dazai was assigned to investigate Yumeno’s ability, and he quickly recognized its extreme danger and volatility. An unspecified incident involving Yumeno caused significant casualties within the Port Mafia, leading Dazai to personally seal them away in confinement. Yumeno remained imprisoned for some time, but during the conflict between the Port Mafia and the Guild, they were released and deployed as a weapon.

Personality-wise, Yumeno displays a deeply twisted and sadistic nature beneath a facade of childish innocence. They can convincingly appear as a harmless child, but they take delight in chaos, suffering, and the carnage their ability causes. Despite this, Yumeno also harbors a strong self-loathing and a hatred for society, peace, and hospitals. Their motivations are driven by a desire to break everything and everyone, with a particular goal of making Dazai suffer for having confined them. This obsession with revenge colors much of their actions.

In the story, Yumeno plays the role of a dangerous and unpredictable asset for the Port Mafia. Their ability is so feared that Dazai considered it the anathema of all other abilities and saw them as a walking disaster. During the Guild arc, Yumeno is abducted by the Guild. The Guild uses them in a devastating plan: John Steinbeck ties Yumeno’s curse to the root system of trees throughout Yokohama, forcing Yumeno to feel every instance of pain the trees experience. This extreme physical and emotional trauma breaks Yumeno’s psyche, causing them to curse the entire city. This moment reveals a tragic vulnerability—Yumeno never wanted their own ability and is tormented by the suffering it brings, both to others and to themselves.

Key relationships are defined by this dynamic. Osamu Dazai is both the person who confined Yumeno and the only one who can nullify their curse with his ability No Longer Human, making him Yumeno’s primary antagonist figure. Within the Port Mafia, Yumeno is feared and kept at a distance; even allies are not safe from their power. The Guild exploits Yumeno as a tool, causing immense suffering and deepening their trauma.

Yumeno’s ability is named Dogra Magra. It is a mind control curse that activates when someone physically hurts Yumeno—specifically by cutting them on the razor blades they tape to their own arms. Once triggered, Yumeno mutilates their doll, and the curse takes effect. A hand-shaped blotch appears on the victim’s body, and they are overwhelmed by horrifying hallucinations that drive them into a murderous frenzy, attacking anyone indiscriminately. The doll regenerates after being damaged, allowing repeated use. The only known counter is Dazai’s nullification upon contact. This ability makes Yumeno one of the most dangerous individuals in the series, capable of turning entire battlefields into chaos. Their development throughout the story shows a shift from a purely sadistic antagonist to a more tragic figure whose hatred is mingled with self-destructive pain and a desperate, broken desire for release.