Under Night In-Birth

The original release of the game included ten playable characters, with two more being added post-launch. The roster currently has a total of 21 fighters as of the release of Under Night In-Birth Exe:Late [cl-r], with two of these being guest characters from other fighting games. The game has Japanese-language voice acting.[11] Some characters later appeared in BlazBlue: Cross Tag Battle, where they received English voice actors for the first time.[12]

• Hyde Kido (城戸 灰都(キド ハイド), Kido Haido): The protagonist of the game. A high school student and one of the survivors of a Void attack. He wields the legendary dark-red magical sword Insulator.
• Linne (リンネ, Rinne): An ancient immortal princess of the Night Blade and the current leading organization of the Hollow Night. She was cursed into a Re-Birth alongside her twin brother and former wielder of Insulator, Kuon (クオン). They were reincarnated in their current host bodies. Her current one is a child who goes to elementary school, where she befriended a girl named Chiharu (チハル).
• Waldstein (ワレンシュタイン, Warenshutain): A hulking wise half-Void and Linne's guardian. He is a former member of the anti-Void organization Licht Kreis back in the day when he was a human, until his defection to Night Blade during a war between two organizations, after Kuon saved him from becoming a Void Fallen.
• Carmine Prime (カーマイン・プライム, Kāmain Puraimu): A young delinquent man with a violent attitude who both Hyde and Seth refer to as a "crayfish", with Carmine referring to them as "clownfish". He uses a strange red substance in battle which he falsely believes to be his own blood, and thus suffers from placebo wherein he feels weakened should he use his powers for too long.
• Orie Ballardiae (オリエ・バラーディア, Orie Barādia): A leader of her team within Licht Kreis whose parents were killed by an intelligent Void. Alongside a girl named Lex Bartholomew, she was sent undercover to Kanzakai under alias of a student "Orie Harada" ("原田 織依"(ハラダ オリエ), "Harada Orie") where she befriends Hyde.
• Gordeau the Harvester (ハーヴスター・ゴルドー, Hābesutā Gorudō, Harvester Gordeau): A mercenary, a bartender, and one of the co-founders of Amnesia, an organization seeking to dominate the Hollow Night. He quits his job, after a freak incident involving the death of a fellow founder, Roger the Survivor (サーヴイヴー・ロジャー, Sābaibā Rojā, Survivor Roger).
• Merkava (メルカヴァ, Merukava): An amnesiac intelligent flying Void accused of killing Orie's parents. He was once a human seeking to become a Re-Birth. Upon his incomplete transformation into a Void, he not only retains part of his form, but survives in daylight with the cost being that his body often makes him hunger for human flesh. Merkava does not use EXS, but a power known as False. Otherwise known as FLS.
• Vatista (バティスタ, Batisuta): Unit code, 10,067. An ancient "Autonomic Nerve" designed as an anti-Void weapon. She is known to lack common sense among human society and will bewilder those around her for not wearing clothes. She used to have a seventh wing, but it transformed into the sword Insulator. Vatista also uses the power of FLS rather than EXS abilities.
• Seth the Assassin (アサシン・セト, Asashin Seto, Assassin Seth): An assassin of the Night Blade. He met Linne when she was under the alias of a young woman, Chitose (チトセ). Seth wields a pair of dark-blue magical daggers Eliminator received from a secret contractor and organization member.
• Yuzuriha (ユズリハ): A not so smart female samurai hailed from the clan and serving the Night Blade. She founded the fighting style Dual Moon Blade Swordsmanship and plans to use the ability to bring peace. Yuzuriha also has a liking to rice crackers.
• Hilda the Paradox (パラドックス・ヒルダ, Paradokkusu Hiruda, Paradox Hilda): The antagonist of the game, leader and one of the co-founders of Amnesia who seeks to become a Re-Birth. She fuses the power of darkness and light. Hilda is known to be an airhead sometimes, along with being a little insane.
• Bloody Chaos (ブラッディ・ケイアス, Buraddi Keiasu): Real name Kei Asuma (明日真 景(アスマ ケイ), Asuma Kei). Amnesia's chief strategist, who can project and manifest the object he obtained. He accompanies Azhi Dahaka (アジ・ダハーカ, Azi Dahāka), a monstrous lizard summoned from the Book of Chaos Code stolen from the Licht Kreis library shortly before joining Amnesia. He is Seth's contractor, and the one who found the daggers Eliminators from an unknown source.
• Nanase (ナナセ): A middle school student who is attacked by a Void and turned into an In-Birth. Not understanding how one becomes an In-Birth, Nanase mistakenly believes Hyde to be responsible for her transformation.
• Byakuya (ビャクヤ): A middle school student accompanied by his "sister", Tsukuyomi (ツクヨミ). In truth, the real Tsukuyomi died in the accident where Byakuya lost his sanity due to his sister complex and became an In-Birth with the powers resembling that of a void. Byakuya eventually meets Strix (ストリックス, Sutorikkusu), a former member of a defunct Demon Society whom he thought her to be his sister's reincarnation, and currently acts as her replacement.
• Phonon the Chermeti (シュメティ・フォノン, Shumeti Fonon, Chermeti Phonon)): Nanase's best friend with a chūnibyō personality. A former member of an In-Birth school club EFG, she received the EXS ability and left the club. Her real name is Yoshiko.
• Mika Returna (ミカ・リターナ, Mika Ritāna): A member of Licht Kreis and a member of Orie's team. She is often very reckless, stubborn and hyperactive to the point she is often punished by those above her by rank as if they are her parents. She is known to have temper tantrums as if she were a toddler. Despite her petite frame, she uses gauntlets almost bigger than her called, Pachelbell Cannon and her EXS abilities are called Diesel.
• Gaien Enkidou (円鬼堂 凱庵(エンキドゥ ガイエン), Enkidō Gaien): A former martial artist and member of Amnesia who prefers to go by the name Enkidu (エンキドゥ). He is bitten by a Void and being granted with a small amount of EXS, with the pair of large shackles on his wrist act as limiters to unleash his full EXS potential in unsealed state for a limited time. He seeks strong opponents to fight to the death.
• Miyashiro Erika Wagner (宮代(ミヤシロ)・エリカ・ワーグナー, Miyashiro Erika Wāgunā): One of the members for Licht Kreis. She is Orie's one sided rival and was sent to school in Japan due to her reckless and albeit, questionable methods on the job, and is the one responsible for Roger's death. Wagner uses the power of fire.
• Londrekia Light (ロンドレキア・ライト, Rondorekia Raito): Wagner's self-proclaimed rival and a member of Ritter Schild, a male only branch organization of Licht Kreis from the result of Waldstein's defection to the Night Blade. He fights with the power of ice.

Guest Characters:

• Sion Eltnum Altasia (シオン＝エルトナム＝アトラシア) from Melty Blood. She is referred to as Eltnum (エルトナム) within the context of Under Night In-Birth. Eltnum is one of the main characters of Melty Blood who has little to no role in the main story. She is often making remarks on all the fighters as if they are novices, while often showing she is self aware of the fact she is a character from the Melty Blood series inside the current game she's in. Even going as far as to mention having appearances in arcades. Specifically, on the Sega Naomi hardware.
• Akatsuki (アカツキ) from Akatsuki Blitzkampf. Akatsuki is the protagonist of Akatsuki Blitzkampf. He has little to no role to the main story. Unlike Eltnum, Akatsuki is in no way self aware and only looking for a way to get back to his duties.