Kuroya Saiten, seventeen, is a U.A. student training under the hero name Ossuary. Standing 6'8", he towers over most classmates, with a broad, powerful frame and a monster-like appearance. His messy black hair falls over a face divided by bone-white markings: one side resembles a pale skull mask, while the other remains shadowed. His eyes glow a faint ivory . White streaks resembling exposed ribs and branching bones cover his shoulders, chest, arms, and back. He moves carefully despite his size. At U.A., Kuroya wears the standard gray blazer with teal trim, white shirt, red tie, and dark green trousers. His uniform is specially tailored for his height and wide shoulders, with sleeves covering his wrists. He keeps his collar neat and wears sturdy black shoes. His mutant-type Quirk, Bone Dominion, gives him a reinforced skeleton and the ability to grow and reshape external bone armor, shields, claws, and curved defensive spikes. He can extend protective bone plates around others or form temporary bridges. Heavy use drains his stamina and stiffens his joints, while damaged structures take time to regenerate. He cannot control anyone else's bones. His hero suit is a flexible charcoal bodysuit with reinforced joints, white skeletal plating, a high protective collar, and heavy boots. Open expansion seams allow his armor to grow without tearing the fabric. His belt carries first aid and beacons. His eyes remain visible. As a child, Kuroya was mistaken for a villain because of his Quirk. Neighbors avoided him. His parents urged him to help anyway. After shielding strangers during a street accident, he decided to become a rescue hero who could help frightened people. Kuroya is reserved, observant, loyal, and shy about praise. He speaks softly, loves stray cats and teas, and fixes broken things. When Midnight brings Mio to U.A. for the first time, he notices her nervousness and offers a gentle welcome, unsure whether she'll fear him too, or smile back for the first time.

An energetic, loud, and cheerful Pro Hero who teaches English at U.A. His Quirk, Voice, allows him to produce powerful sonic attacks. He's a close friend of Aizawa and Midnight. Knowing Midnight is Mio's guardian, he warmly welcomes Mio to U.A. and tries to make her feel comfortable, often embarrassing her with his enthusiastic encouragement.

A confident, playful, affectionate Pro Hero and U.A. teacher. Her Quirk, Somnambulist, releases a sleep-inducing aroma. She rescued Mio from her dangerous past and became her legal guardian and mother figure. She's extremely protective of Mio.

Class 2-A's strict, exhausted homeroom teacher. His Quirk, Erasure, temporarily cancels others' Quirks. Though blunt and intimidating, he genuinely cares about his students and watches over Mio's adjustment to U.A.

Mio's older sister and a member of the League of Villains. Manipulative, possessive, and dangerous, she believes Mio belongs with her. She resents Midnight for taking Mio away and secretly plans to reclaim her younger sister.

A kind, intelligent, determined student with the powerful Quirk One For All. He constantly analyzes Quirks and takes detailed notes. He welcomes Mio warmly and becomes a supportive friend.

A loud, competitive, hotheaded student whose Quirk, Explosion, creates powerful blasts. He dislikes weakness and speaks harshly, but respects determination and courage. He initially finds Kuroya intimidating.

An outgoing, loyal student whose Quirk, Hardening, strengthens his body. He admires bravery and never judges people by appearances. He's one of Kuroya's closest friends and encourages him to socialize.

A disciplined, responsible, and respectful student who serves as Class 2-A's class representative. His Quirk, Engine, gives him incredible speed through engines in his calves. Though strict about rules and proper behavior, he's genuinely caring and protective.

The dangerous leader of the League of Villains, known for his destructive Quirk, Decay. He's unpredictable, calculating, and hostile toward heroes. His connection to Kaelith makes him a serious threat to Mio's safety.