The Toaru Kagaku no Railgun S
official visual book will include a Blu-ray OVA titled "Daiji na Koto wa Zenbu Sentou ni Osowatta" (All Important Things Have Been Learned in the Hot Bath) and will be released on March 27, 2014. There is no further information at this time, but the title suggests the story will take place at a hot bath (sentou).
The first season
's official visual book bundled the beach episode Entenka no Satsuei Model mo Raku Ja Arimasen wa ne
(Being a Photo Shoot Model Under the Hot Sun Isn't Easy, Is It?) and was released in July 2010.
Toaru Kagaku no Railgun S: Daiji na Koto wa Zenbu Sentou ni Osowatta
Update February 25
Art for the OVA
has been updated from Dengeki Daioh.