Toaru Kagaku no Railgun S OVA

All the Important Things I Learned in a Bathhouse (大事なことはぜんぶ銭湯に教わった) is the first OVA for the Toaru Kagaku no Railgun S anime series. It was first released on March 25, 2014, bundled together with the Toaru Kagaku no Railgun S official visual book.

Synopsis
While trying to figure out what to do with their free time, the girls come upon Mii handing out flyers for a classic public bath in School District 7. Apparently, the public bath is in trouble as no one is coming there anymore, and Mii is helping out because the bath has sentimental value for her when she was younger, specifically during her time as a member of Big Spider.

The girls brainstorm on what to do, with Mikoto saying to put Gekota toys in the bath, while Ruiko suggesting in making up and spreading an urban legend about tossing coins into the bath to become prosperous or finding true love. Kuroko however suggests of using Mikoto's powers for an electric bath, and everybody is inclined to agree. Mikoto eventually acquiesces to her suggestions. They later help out on promoting this novel idea.

It works and the bath becomes popular with women. However, Kuroko goes overboard after pulling out a liquid soap form nothing, flooding the bath with foam, and forcing Mikoto to shock Kuroko as punishment. The guests later leave and the girls give them a complimentary Musashino milk to go.

The girls then have the bath all to themselves, except Kuroko which is tied up and becomes increasingly erratic as she overhears the girls trying to watch other, especially Mikoto. Mikoto later eventually frees her, on the one condition that she does not remove her blindfold. However, this does not prevent her from being perverted, causing Mikoto to shock her again.

After the bath, the girls themselves decide to drink Musashino milk. They however, notice that every time Mii drinks milk her breast moves, eventually it escapes the confines of Mii's towel, much to her embarrassment. The girls notice this, and they all recall the times Mii has been drinking the milk. Seeing that they want to enlarge their chests, the girls gather bottles of Musashino milk, and begin drinking in a frenzy. It doesn't go quite well.

Adapted From
This is an anime original video animation, as such it is not based on any pre-existing material.

Characters
By order of appearance
 * Misaka Mikoto
 * Saten Ruiko
 * Uiharu Kazari
 * Shirai Kuroko
 * Konori Mii
 * Tokiwadai Dorm Supervisor
 * Yomikawa Aiho
 * Wannai Kinuho
 * Awatsuki Maaya
 * Kongou Mitsuko
 * Tessou Tsuzuri
 * Tsukuyomi Komoe
 * Haruue Erii
 * Edasaki Banri
 * Mugino Shizuri
 * Kinuhata Saiai
 * Takitsubo Rikou
 * Frenda Seivelun

Abilities

 * Teleport - Shirai Kuroko, Level 4
 * Railgun (ability) - Misaka Mikoto, Level 5

Locations

 * Academy City
 * School District 7
 * Pasticceria Manicagni (referenced)

Trivia

 * The location where the girls find Mii handing out the flyers is the same place where they found Febrie back in episode 18.
 * The public bath that has been featured several times in the anime is apparently located in School District 7.
 * The only non-antagonistic characters of the same age group that has actually appeared in Toaru Kagaku no Railgun S that does not appear in this episode are Nunotaba Shinobu, Yanagisako Aomi, and Edasaki Banri.
 * Despite Saten Ruiko having been featured having larger breasts than the other three girls in their group many times in previous episodes, even earlier in this episode, she is shown to want larger breasts here. This emphasized here where she has the same bust size as the others at the end. This continues the trend of the anime adaptation's inconsistent depiction of Ruiko's breast size.

Quotes

 * Mikoto and the others: "After all, if it's going to be milk... then it has to be Musashino Milk!"