Speed-o'-Sound Sonic originated in the Ninja Village, enduring its brutal training as part of the 44th Graduation Class, infamously known as "The End." As a child, he deliberately underperformed to experience the harshest regimens alongside classmate Flashy Flash. During this period, Sonic harbored ambitions to reform the village, advocating for greater trainee freedom and envisioning a kinder future for ninja education. A pivotal tragedy unfolded when Blast, targeting the village's corruption, massacred most of the class. Sonic survived through his own strength, an event that profoundly warped his worldview and fostered deep cynicism toward heroes and institutions. Physically, Sonic is a 25-year-old human male standing 5'9" (1.74 m) and weighing 64 kg. He possesses long black hair, typically secured in a topknot, gray eyes, and distinctive purple markings beneath them. His standard attire is a black bodysuit featuring metallic plating on the limbs and torso, accented by a long purple scarf. This appearance temporarily altered after Genos severed his topknot in battle, though his hair later regrew. Sonic's personality blends arrogance, bloodlust, and fierce competitiveness. He openly disdains heroes, viewing them as hypocrites, and takes pride in never sparing opponents. Despite this ruthless exterior, he demonstrates flickers of compassion, such as warning Genos about the Deep Sea King or bonding with a piglet named Ino during training. His fixation on defeating Saitama borders on obsession, driving him to extreme measures like consuming a Monster Cell; cooking it negated its effects, resulting in severe diarrhea instead of monsterization. A master ninja, Sonic's core abilities revolve around supersonic speed, agility, and ninjutsu. Key skills include: - **Afterimage Creation**: Progressing from Two Shadows Burial to Thirteen Shadows Burial, generating multiple illusions to confound opponents. - **Specialized Attacks**: Techniques like Wind Blade Kick, Exploding Shuriken barrages, and the Speed of Sound Electric Discharge Fist, delivering lethal electric shocks. - **Enhanced Physicality**: Superhuman reflexes, durability (honed by surviving Saitama's punches), and strength allowing effortless limb dislocation. His growth trajectory is significant; initial defeats by Saitama spurred intense training, enabling him to later clash evenly with S-Class hero Flashy Flash, withstand techniques like Flashy Kicks, and resist Empty Void's psychological manipulations through sheer willpower. Sonic wields traditional ninja weaponry: kunai, explosive shuriken, and a ninjato. He later acquired one of the Legendary Demon Swords after Saitama distributed them, enhancing his combat capabilities. His story intersects with major events: - Early encounters with Saitama began during the Paradise Group Arc, where Sonic's defeat ignited their rivalry. He was later imprisoned after causing urban chaos to provoke Saitama. - In the Sea Monster Arc, he fought the Deep Sea King unarmed, retreating only when the monster transformed in the rain. He returned too late, as Saitama had already defeated it. - During the Monster Association Arc, he rejected Monster Cells after his initial failure but later trained rigorously, achieving parity with Flashy Flash. Together, they battled the Heavenly Ninja Party and confronted Empty Void. - Post-Alien Conquerors Arc, he investigated remains of Boros's ship. In the Neo Heroes Saga, he eliminated Neo Heroes agents sent to assassinate him. Sonic operates as an S-Class criminal and occasional mercenary, though his actions occasionally align with heroics, such as aiding Flashy Flash against existential threats. His enduring rivalry with Saitama remains central to his motivations, yet he refuses to fight Saitama during the hero's battles with monsters, acknowledging an unspoken respect.