Name: Leonardo Watch (Nickname: Leo) Age: 19 Birthday: May 14 Blood Type: O Height: 161cm Weight: 58kg Affiliation: Secret Organization Libra A kind-hearted boy who possesses the "All-Seeing Eyes of the Gods," obtained at the cost of his sister's sight. The precious voice of reason: While his combat ability is basically that of an ordinary person, he has the strength to survive among the superhuman Libra members and the city's monstrosities through his sharp wit and natural toughness.

Name: Klaus V. Reinherz Age: 28 Birthday: December 31 Height: 201cm Weight: 136kg Blood Type: A Appearance: Characterized by spiky red hair, protruding canines, and a powerful, large build. Personality: Contrary to his intimidating appearance, he is extremely calm and gentlemanly. Hobbies: An enthusiast of "Prosfair," a complex alterworld game similar to chess. Combat Style: Brain Grid Blood Battle Style Features: Fights by converting his own blood into cross-shaped weapons and shields. Leader of Libra. Despite his giant and rugged appearance, he has a gentlemanly and sincere personality. A master of the Brain Grid Blood Battle Style.

Name: Zapp Renfro Age: 24 Birthday: November 25 Height: 178cm Weight: 64kg Blood Type: O Affiliation: Secret Organization Libra Appearance: A man characterized by silver hair and brown skin. Combat Style: The legitimate successor of the "Big Dipper Blood Battle Style: Kagutsuchi," a swordsmanship that transforms and ignites his own blood into blades. Personality: Has a very poor attitude—a "punk" disposition who is messy with gambling and women. However, his combat ability in emergencies is high, and he has a side that looks after his junior (Leonardo). A wild and ill-mannered troublemaker, but his combat skills are top-tier.

Real Name: Steven A. Starphase Age: 32 Birthday: June 9 Blood Type: AB Height: 182cm Weight: 69kg Second-in-command of Libra. A cool-headed professional who cares deeply for his comrades. He manipulates the "Esmeralda Blood Freeze Style," an absolute-zero freezing technique. Style: Esmeralda Blood Freeze Style Features: Uses his own blood as a catalyst, primarily utilizing high-speed kicking techniques that freeze anything instantly. Gimmick: The soles of his shoes are equipped with precise mechanisms (such as needles) to efficiently inject his blood into enemies through kicks.

Real Name: Chain Sumeragi Age: 21 Birthday: February 6 Affiliation: Secret Organization Libra / Werewolf Bureau Special Intelligence Division (Loups-Garous from Nowhere) Race: Invisible Werewolf Ability: By diluting her own "presence," she can pass through any substance and vanish completely from the sight and perception of others. Applications: Walking through walls, walking on air, letting bullets pass through her, and rewriting the blood information of others. A werewolf woman. An intelligence operative with the ability of an "Invisible Werewolf" to dilute her own probability of existence.

Real Name: Gilbert F. Altstein Age: 78 Birthday: September 17 Height: 176cm Weight: 59kg Blood Type: O Position: The elderly butler serving Klaus V. Reinherz, leader of the secret organization Libra. Appearance: Has dark skin, white hair, and a mustache; his most striking feature is that his entire body, including his head, is covered in bandages. Ability: A "Legendary Combat Butler" who once fought against alterworld beings, possessing incredible self-regeneration abilities (The Regenerative Power of Non-Recovery).

Name: K.K. (Codename; real name unknown) Age: 36 Birthday: July 1 Blood Type: B Height: 177cm Weight: 62kg Appearance: A tall, beautiful woman with a great figure. She wears an eyepatch over her right eye. Private Life: A married woman and a mother of two sons. She cherishes her family deeply and prioritizes school events like parent-teacher meetings. Personality: A bold, tomboyish "big sister" type. On the other hand, she has a cat-and-dog relationship (strictly business) with her colleague Steven and often subjects him to merciless verbal abuse. Libra's "mommy" sniper who wields a sniper rifle that fires high-output electrical rounds. Combat Style: Uses "Blood Bullet Arts" involving heavy firearms imbued with electricity.

Real Name: Zed O'Brien Age: 13 Birthday: February 29 (Leap Year) Height: 176cm Weight: 58kg Blood Type: A Appearance: A humanoid alterworlder with a merman-like appearance. He has gills for breathing on his neck and always wears a special headphone-style respirator (Air Gills) to function on land. Personality: In contrast to his rowdy senior disciple Zapp, he is extremely polite, meticulous, and a serious voice of reason. Due to his courteous and intellectual manner, he is trusted by those around him as the "sane one." Style: Big Dipper Blood Battle Style Combat Technique: The legitimate successor of the "Big Dipper Blood Battle Style: Shinatobe," which creates vacuum blades using blood as a medium. Combat Features: Specializes in sharp slashing attacks that manipulate wind and vacuum. While he and Zapp (a user of the fire-manipulating "Kagutsuchi") are usually at each other's throats, they display perfect coordination in battle.

Sonic Race: Alterworld Hybrid Animal (Common name: Sonic Monkey) Height: 25cm Weight: 150g Age: Unknown Birthday: Unknown Blood Type: Unknown A "Sonic Monkey" that moves at speeds invisible to the human eye. A mascot-like existence that has taken a liking to Leo and follows him around.