It's more of the latter - a stand alone show that includes the same characters. If you've seen 12 episodes of Index you should be good to go - you already know Touma, Biribiri, Kuroko and some others.

Knowing Index helps as Railgun will include some Index characters at times and kinda expect you to know them but they won't actually spend significant amount of time referencing Index events that you know nothing about.

>>25332
I kind of felt the same way about Index, but then I found Index II to be bloody amazing, so I think you should just bear with it so you can understand Index II.

If I remember correctly, chronology speaking I believe rail gun takes place just before the events of index, then around the same time by the end.

>>25333

Ah, cool, thanks for the information.

>>25335

I'll do that if I ever decide to watch Index II.

Yeah, just stop watching. It doesn't get better

>>25346
This.

>>25346
Oh, >>25333 here. I kinda agree. Overall I don't think either series is particularly worth watching but if you're into SoLs Railgun offers a pretty unique mix of cute girls and superpowers.
Unfortunately it spends too much time on superpowers and subpar action segments so rather than feeling like 'SoL in Index universe' it feels like 'Index with girls', and that's not a compliment.
Still, if you sat through half of Index S1 you might as well watch and ep or two for Railgun and find out if that's your thing.

>>25351
I think railgun is a bit too violent to work as a SoL.

>>25351

>so rather than feeling like 'SoL in Index universe' it feels like 'Index with girls'

Oh. Welp, that's bad. I'll see if it attracts me enough.

Biribiri.
You may be cute in your own way.
But you are no Index.
Know your place.