USApyon, also known as Usapyon, is a 'Merican yo-kai from the United States. Originally an otter named Danny or Chibi, he accidentally entered a rabbit pen. Bullied for his differences and living in loneliness, he was eventually adopted by scientist Doctor Hughly or Professor Hyuri. The professor planned to send him to space. During a rocket engine test, Danny panicked, touched an electrical circuit board, and perished in the explosion. This event transformed him into the yo-kai USApyon, driven by his dream of space travel and finding the professor. He appears as a small, otter-like creature with light blue fur, typically clad in a yellow spacesuit featuring rabbit-ear-like protrusions on the hood, a reference to his past. He wields an orange ray gun shaped like a carrot, the "Bunny Blaster," and wears a blue jet pack with a wispy, smoke-like purple tail. When angered, USApyon activates "Invader Mode" (or Vader Mode), manifesting a dark visor over his face, smoke filling his helmet, and glowing red eyes. At peak fury, he becomes "Emperor Mode," gaining red or pink armor, a teal-green cape, enhanced strength, and flight, with his gear changing color accordingly. Without the suit, he resembles an otter wearing a red scarf patterned with stars and stripes and black shorts marked "USA." Personality-wise, USApyon is serious, ambitious, and highly intelligent, especially in rocketry and space technology. He possesses a quick temper, easily provoked into Invader Mode where he fires laser beams indiscriminately. Despite his volatility, he forms deep bonds, showing immense respect for Doctor Hughly and genuine, though often masked, care for his human partner, Hailey Anne Thomas (Inaho Misora). His fear of solitude stems from pre-yo-kai isolation. He persists stubbornly in his goals and avoids admitting fault until confronted with evidence. His primary ability involves the Bunny Blaster, firing electrical or laser beams that can inspirit humans or damage foes. Invader Mode increases his aggression and firepower, while Emperor Mode grants flight and significantly enhanced combat strength. USApyon utilizes specialized gear altering his elemental attributes: Football Gear (Fire/Lightning), Scuba Gear (Water), GI Gear/Survival Gear (Earth), and Racing Gear (Lightning/Wind), providing tactical advantages for space travel preparation. His story begins when he encounters science-fiction enthusiast Hailey Anne, tricking her into getting the Yo-kai Watch U Prototype. He enlists her help to locate Doctor Hughly, finding the professor hospitalized and despondent over the failed rocket test. To rekindle Hughly's spirit, they build a model rocket, leading to the establishment of the InaUSA Detective Agency in Sparkopolis to investigate yo-kai incidents. The agency operates episodically, closing temporarily after resolving cases like the Phantom Thief Kopin affair before reopening. His relationship with Hailey Anne is contentious yet devoted; he frequently blasts her into Invader Mode due to her antics, like breaking his rocket models, but relies on her partnership and shares mutual loyalty. Their dynamic involves rebuilding rockets and navigating conflicts, often requiring mediation from Nate Adams and other yo-kai. He shares camaraderie with Tomnyan, another 'Merican yo-kai, bonding over shared origins and enjoying his music. He initially finds Jibanyan peculiar but collaborates with Nate, Whisper, and Jibanyan during stays at Nate's house, annoyed by Whisper's name mispronunciations. Cross-media appearances show him assisting against threats like Wobblewok or Snippity Crickets, using Soultimate moves, sometimes with unintended consequences like growing enormous. His background as a test subject resurfaces when recalling being caged and fed on command, contrasting his initial belief of good treatment.