This second episode of To Aru Kagaku no Railgun kicks off with a brief cameo for To Aru Majutsu no Index's Touma.... However, a cameo is all it is, so don't go expecting too much based off that opening scene.
From here, the rest of the episode takes on a decidedly "slice of life" flavour, prferring to focus entirely on Mikoto and Kuroko on the one month "anniversary" of their becoming room-mates. Needless to say, this makes the episode all about Kuroko trying to find ways to seduce Mikoto and failing miserably, with her plans for a "quiet" night in with Mikoto ruined by the appearance of Uihara and Saten, in a state of affairs that leads to them both using their powers in the dormitory and being punished for doing so, moving the episode on to a bout of swimming pool cleaning where the two of them make up... well, somewhat at least.
There's not really a lot more to say about this particular instalment of To Aru Kagaku no Railgun - I'd almost be tempting to label it as filler, but I'm not even sure what the actual goal of this series is yet. If it's going to be a simple, non-stop fan service-fest based around Mikoto and Kuroko then I guess this isn't a filler episode at all, but to be honest I'm really hoping that it has more strings to its bow than that.
I will concede however that this episode was actually quite fun to watch (dare I refer to it as "fan service done right"?) as a one-off in its own right, but if it's going to keep my interest then this series is going to have to remember the expert blend of fun every-day moments blended with bigger, more action-centric story arcs which To Aru Majutsu no Index frequently carried off quite effortlessly. I mean come on, you have a protagonist who can shoots coins at you at ridiculous speeds using the power of electricity, you can't just have her electrocuting over-excited fangirls for an entire series.