Speed-o'-Sound Sonic, also known simply as Sonic, is a human male ninja from the secretive Ninja Village, an institution dedicated to training elite assassins. He trained within the 44th Graduation Class, nicknamed "The End," alongside Flashy Flash. During their youth, Sonic and Flashy Flash bonded over their shared disdain for the village's brutal methods and mutual desire for greater freedom. Sonic aspired to become the highest-ranking officer to reform the village into a kinder system for future trainees. Nine years before the main events, the hero Blast attacked the Ninja Village, massacring nearly all trainees. Sonic emerged as the sole survivor of his class, an experience forging his cynical worldview and deep distrust of heroes. This trauma contributed to his path as an S-Class criminal, though he holds no grudge against the similarly surviving Flashy Flash. Physically, Sonic is a slim man of average height (5'9" or 1.74 m) with long black hair typically tied in a topknot and bangs framing his face. Distinctive purple marks appear beneath his gray eyes. His standard attire is a tight black bodysuit featuring metal plating on the shins, forearms, shoulders, and chest, complemented by a long purple scarf. He carries a ninjato, kunai, exploding shuriken, and other specialized ninja tools. Sonic's personality blends arrogance, competitiveness, and a fervent love for combat. He declares Saitama his eternal rival after their first encounter, relentlessly challenging him despite repeated defeats. He disdains heroes as hypocrites who "pretend to fight for justice" and initially shows little regard for human life, taking pride in never sparing opponents. However, glimpses of a softer side emerge through his friendship with bear hunter Frank and his adoption of a piglet named Ino during training, revealing capacity for empathy and loyalty. His cynicism extends to organizations like the Hero Association and Neo Heroes, which he considers corrupt. Sonic's primary abilities center on superhuman speed, agility, and reflexes, enabling movement faster than the eye can track and the creation of afterimages to confuse opponents. His techniques include: - **Shadow Burials**: Generating afterimages (initially four, later ten, and eventually thirteen) to disorient foes. - **Wind Blade Kick**: A spinning kick utilizing momentum for increased force. - **Exploding Shuriken**: Homing projectiles detonating on impact. - **Speed of Sound Electric Discharge Fist**: A finger thrust releasing lethal electricity. He possesses enhanced strength and durability, the latter attributed to surviving Saitama's punches. Observers like Fubuki consider his combat prowess S-Class level. Key story developments include: - **Early Encounters**: Working as Zeniru's bodyguard, he first battles Saitama while targeting the Paradisers. A humiliating defeat (including a punch to the groin) sparks his obsession with surpassing Saitama. - **Imprisonment and Deep Sea King Fight**: Escaping prison during the Sea Monster arc, he fights the Deep Sea King unarmed, dodging attacks effortlessly but retreating after its transformation. He later warns Genos about the threat. - **Rivalry Escalation**: He interrupts Saitama's battle with Genos, leading to a stalemate against the cyborg. He demonstrates "Ten Shadows Burial" against Saitama only to be swiftly defeated again. - **Monster Association Arc**: Offered a Monster Cell by former classmates Gale Wind and Hellfire Flame, he cooks and eats it hoping for power but suffers severe diarrhea, as cooking nullifies the cell's effects. - **Neo Heroes Saga**: Confronting Neo Heroes agents sent to eliminate him, he defeats them with his electric discharge technique. He later observes Saitama's fight with Tatsumaki and attempts an ambush with homing shuriken, which are deflected. Sonic's relationships are defined by rivalry and reluctant camaraderie. His fixation on defeating Saitama drives much development, though he respects Saitama enough to avoid interfering during the hero's battles with monsters. His dynamic with Flashy Flash evolves from shared childhood ideals to a tense alliance against the Heavenly Ninja Party, showcasing their synergistic combat abilities despite their history.