Misaka and Kuroko at the beach is exactly what you want it to be: no pretense, no plot getting in the way, just their dynamic doing what it does best. The show trusts you already love these characters enough that watching them exist in swimwear is entertainment on its own. Four minutes of fanservice that doesn't apologize for being fanservice, bundled with a visual book because this is made for people who already paid to be here.

Misaka and her friends keep enjoying themselves at a swimsuit company's beach simulator in this single comedy OVA episode with ecchi touches. Uiharu starts applying tanning oil to herself, and Misaka asks if she can join in. Kuroko, jealous that Misaka is paying so much attention to Uiharu, comes up with a plan of her own. The special is a beach episode that was bundled with the official Toaru Kagaku no Railgun visual book and is counted as episode 13'.