Talk:Shinyaku Toaru Majutsu no Index Light Novel Volume 09/@comment-31669652-20141217153106/@comment-34962159-20180915111324

It's in the Omega World, though she's not mentioned by name.

''“Oh, Uiharu. I just remembered. Is it true Arisa-chan is coming here in secret today? Y’know, that ‘perfect mode’ created once the two became one.”''

The speaking style and the context of this line suggest that Saten is saying it.