Yomikawa Aiho

Yomikawa Aiho (黄泉川 愛穂) is teacher at Touma's school and a friend of Komoe. She is beautiful, has glamorous proportions, and is always seen with a green jersey and often ends her sentences with "-jan". Despite having a glamorous figure, she acts in a tomboyish matter and regularly joins colleague Tsukuyomi Komoe in drinking sessions after their work. She also always teases Komoe, her senior & friend.

Background
She is a member of Anti-Skill and cares deeply for her students (in spite of having a "spartan" approach in teaching according to Komoe), and is an active peacekeeper within Academy City. Due to her habit of ramming delinquents with protective items like shield or helmets to resolve incidents, saying it's alright to do so since those are protective items, she's known as 'the woman who uses comedy-like methods to solve problems that could end up as a tragedy'.

As a favor to her old friend, Yomikawa is asked by Yoshikawa Kikyou to take care of Accelerator and Last Order after they are released from the hospital.

Yomikawa suspects that Accelerator is involved in Academy City's dark side, which he does not deny, but instead calls Yomikawa naive for thinking the things that barely scratch the surface are the worst that things can get. Later she brought Accelerator back out of the dark side briefly, before he got dragged back by Kakine and got herself stabbed by Dark Matter.

Kazakiri Hyouka Arc
She first seen talking and teasing Komoe about her student Kamijiou Touma. She is later called to capture the intruder Sherry Cromwell. Despite their best efforts, they are no match for her. However, Touma is able to provide them with assistance in defeating her.

Tree Diagram Remnant Arc
She is briefly seen guarding the bathroom that Accelerator and Last Order are using to bathe.

Diahasei Festival Arc
She meets Touma and Index when she blocks their way from crossing the street. She told them that they would have to take the long route in order to get across, much to Index's dismay.

Academy City Invasion Arc
She takes on the role of Accelerator and Last Order's guardian along with her friend Yoshikawa Kikyou, and she lets them all stay in her apartment. Accelerator tries to warn her that it might not be the best idea to let him stay with her, but she tells him that she does not mind. She also tells him that he may not be as bad as others said he was.

She later assists Accelerator in attempting to find Last Order. While doing so, she has a heart-to-heart conversation with Accelerator regarding his past which seems to have some affect on Accelerator.

During Vento's invasion of Academy City, she is affected by Vento's "Divine Punishment", due to her hostility towards "the one attacking Anti-Skill". She is later found by Kikyou who is unsuccessful in waking her up. After Touma defeated Vento, Aiho was eventually freed from the "Divine Punishment's" curse.

Skill-out Uprising Arc
In the aftermath of the invasion, she states that Accelerator left her home because unbeknownst to her, Accelerator was forced to join GROUP. Her duties as an Anti-Skill have increased due to the need to increase security for the impending war. However, she also states that while they have increased security at Academy City's borders, this has also caused the Skill-out to become more ambitious in their own goals.

During the Index II finale, she is seen having a conversation with Kikyou and Komoe.

Terra of the Left and Document of Constantine Arc
Aiho was forced to perform a power suit demonstration for investors from outside Academy city at the start of the arc. Aiho noted how it was terribly uncomfortable to pilot a power suit while wearing an Anti-Skill bullet-proof armor vest to which the scientist monitoring the suit's operation answered that Yomikawa could have perfectly choose to pilot the suit wearing a bikini if she so desired.

Battle Royale
She is reunited with Accelerator after she witnesses him defeating Kakine for the first time; she manages to convince Accelerator to let go of the gun and spare Kakine, but she is stabbed by Darkmatter which infuriates Accelerator. Luckily, Aiho was able to survive.

Dragon (=/ Angel)
Accelerator broke into her apartment and took Last Order away with him and left her a note. Afterwards, Accelerator broke his only link to her as well as any other people in his life by destroying his phone.

Freshmen Attack Arc
In New Testament, when Accelerator came back, it was said that she punched him and then hugged him. She also tried to stop an argument between Last Order and Yoshikawa over a breast enlarging device, but somehow ended up getting involved herself.

Quotes

 * "'Do you know who it is standing there?! That is a child that we must protect! Pointing guns at children, I’ll never agree! How could I possibly agree to something like this!!” -- Said in Vol15 to prevent Anti-Skills attacking Accelerator.
 * U-umm.. This is Yomikawa Aiho of Anti-Skill Branch 73. With charges of theft, property damage, attempted murder, and interference with a public servant's duties, I'm taking you pieces of shit down to Hell!!" -- Said in SS Volume 2, chapter 1 while she was chasing Hamazura Shiage, Komaba Ritoku and Hattori Hanzou