Toaru Majutsu no Index Wiki
Pentagram-GreatGold Series Three Overhaul Project
This article will be undergoing extensive revision as part of a wiki-wide overhaul

Houjou Arei (北条彩鈴 Houjou Arei?) is a student of Tokiwadai Middle School, who appears in Toaru Kagaku no Railgun: Astral Buddy.[4][1][5][6][7]


Arei has red eyes and messy black hair which she ties in ponytail. In her first appearance, she wore a Tokiwadai jacket. Underneath she wears her full body suit along with her skirt.[4][6]


Normally stoic in her expression, she is however quite merciless when it comes to her enemies, beating down Makigami Komaki so much that even Yumiya Iruka showed concerned that she was overdoing it.[4] She also enjoys it when her opponent is strong enough for her in battle, as with the case with her fighting Hokaze Junko, after she momentarily bested her and making her bleed from her nose.[5]

In spite of this she does value her friend Iruka, as she concedes to her wishes even if interrupts her love for battle,[5] and shows concern over her well-being especially when it came to their plan against Junko and Shokuhou Misaki.[8] After her escape and Iruka's capture with their mutual defeats from Junko, Arei tries to fulfill Iruka's wishes of wanting people to admire Junko, and describes her as an older sister who loved her little sister. Indeed, she hoped that Iruka would take a different path than her and her boss.[8]

Later during her interactions with her older brother, Houjou is shown to have a more tender side to her personality, as seen where she was mildly annoyed and embarrassed by her brother's teasing and care for her and even blushed slightly as she annoyingly told him that she wasn't a child anymore, showing a close familial relationship with him.


Houjou sibling flashback - Astral Buddy Ch26

A young Houjou Arei with her older brother Seigo

Not much is known about her past, though it is shown that she practiced using kunai on target practices when young.[3] According to Nogi Yasuhito, she belongs to certain ninja clan which has been exterminated and is extinct in the present.[2][Notes 1]

Before entering Tokiwadai, she belonged to another middle school. Despite being a Level 2, she was accepted into Tokiwadai as a technical exchange student because her highly specialized skills and abilities were considered equivalent to a Level 3.[3]


Astral Buddy[]

Astral Buddy Arc[]

Main article: Astral Buddy Arc
This section requires expansion


Her ability is called Whisper Bell (感情音叉ウィスパーベル Kanjō Onsa (Uisupā Beru)?, lit. "Emotional Tuning Fork").[3] It allows her to hear people's emotions as sound. She has trained herself to interpret this emotional sound as locations, directions and distance in 3D space.[1] She is only Level 2, but because of her highly specialized skills and her ability to apply her power she was considered to be equivalent to a Level 3. Because of this, she was allowed to enter Tokiwadai Middle School.[3]


During her last battle with Hokaze Junko, she made use of Hard Taping Custom (発条包帯・改ハードテーピング・カスタム Bane Hōtai Kai (Hādo Tēpingu Kasutamu)?) and an electric potential elastic suit to strengthen her physical abilities.[1] This also allowed her to move about even after being beaten by Hokaze Junko.

In her battle against Shirai Kuroko and Shokuhou Misaki, she utilized kunais.[9]


  1. Nogi says the Houjou family name is a hint. Based on her name, Houjou is a "Fuma" (風魔?) ninja since they served the Houjou clan in Feudal Japan.



v  e
Tokiwadai Middle School
Students (Current Year)
Misaka Shirai Kuroko Winter Clothing (Anime) Shokuhou Misaki in Winter Clothing (Anime) Hokaze Junko Winter Clothing (Anime) Kongou Mitsuko in Winter Clothing (Anime)
Misaka Mikoto[1] Shirai Kuroko Shokuhou Misaki[1] Hokaze Junko[1] Kongou Mitsuko
Awatsuki Maaya RailgunT (Anime) Wannai Kinuho RailgunT (Anime) Kirifu Megumi (Anime) Kobayashi Satori (Anime) Yumiya Iruka Color (Astral Buddy)
Awatsuki Maaya Wannai Kinuho Kirifu Megumi[1] Kobayashi Satori[1] Yumiya Iruka
Houjou Arei (Astral Buddy) Makigami Komaki (Astral Buddy) Maybe Natsumi Sakibasu Yuri (Navbox) Gaouin Tsukasa
Houjou Arei Makigami Komaki Natsumi Sakibasu Yuri Gaouin Tsukasa
Kamino Kokuchou Mayui Iori Mashiro Tatsuki Mirei Kumamori Tazuna
Kamino Kokuchou Mayui Iori Mashiro Tatsuki Mirei Kumamori Tazuna
Inubushi Glasses Judgment Girl - Commissioner (Mental Out) Mei (Anime) Kii (Anime) Resanerié Sadis Dialine
Inubushi Glasses Judgment Girl Mei Kii Resanerié Sadis Dialine[1]
Asato Kisa (Anime) Mibuki Kazan (Anime) Spy in Shokuhou Clique Otonari Hibiku
Asato Kisa[1] Mibuki Kazan[1] Nenohi Wakana Otonari Hibiku
AndouIkushimaInoriKinoshita HagoromoMatsuzai ShoukoSenbayashi KonomiTanaka MizuhoUmibe RyoukoUsukinu YasumiYonaki ReikaYamashiroYanagisakiin RondoYugure Kanaria
[1]: Student who is also present in Tokiwadai 1 year ago.
Students (1 Year Ago)
Kessai Kiyoshi (Navbox) Shinenkouji Rurikakesu Sha Tanshan Mikagami Nagisa Hasekura Reiri
Kessai Kiyoshi[C] Shin'enkouji Rurikakesu[G] Sha Danshan[C] Mikagami Nagisa[G] Hasekura Reiri[G]
Lily Ouyang Qian Lin Lihua Urui Aika Kazanin Tsukasa
Wu Lili Ouyang Qian Lin Lihua Urui Aika[G] Kazan'in Tsukasa[G]
Asakura Olivia Moa Kadosaka Rina Sukezawa Sena Enjou Kasumi Yasutoba Suika
Asakura Olivia Moa[G] Kadosaka Rina Sukezawa Sena Enjou Kasumi Yasutoba Suika[G]
Amano Ayane Unnamed Hasekura Clique Member 1 (Railgun Ch139) Unnamed Hasekura Clique Member 2 (Railgun Ch138) Unnamed Hasekura Clique Member 3 (Railgun Ch138) Ibotanokikouji Kaede
Amano Ayane[G] Satsuki Mahiru Soyogo Kato Asuwara Yui Ibotanokikouji Kaede[D][F]
For the unnamed clique members, see respective pages: Sha Clique, Mikagami Clique, and Hasekura Clique.
[C]: Student who is present in current year. / [D]: Deceased / [F]: Former student who haven't graduated but left school / [G]: Graduated
Students (2 Years Ago and Earlier)
Takebayashi Yayoi
Takebayashi Yayoi[D][F]
[D]: Deceased / [F]: Former student who haven't graduated but left school
Unabara (Mental Out Ch20, 6D+6F) Ryoukan Watanabe (Anime)
Director Unabara
Tokiwadai Dorm Supervisor Watanabe
v  e
Kouga School
Oumi Shuri (Railgun) Tsurigane Sugitani Profile
Oumi Shuri Tsurigane Saryou Sugitani
Maybe Sakata Maybe Asai Yasu Railgun
Sakata Asai Yasu
Hattori Clan Iga Clan Fuma Clan
Hattori Hanzou Novel Kuruwa Novel Houjou Arei (Astral Buddy)
Hattori Hanzou Kuruwa Houjou Arei