I'm not 100% convinced yet, personally, but it is looking likely. There's a ton of information that we're not privy to that someone would look up IRL. Like how old Akemi's account is, etc. I'd be digging around search engines like crazy just to make sure. Yamato doesn't do any of that (because it would kill the plot). Plus, we have no idea what Mio does in her free time when Yamato is away at work and she's not streaming.
Personally, I'd love to see Yamato take more initiative and dig. I suggested spy cameras (and maybe a phone app to read Mio's messages) around the house when she's not aware. Or have it be another choice of telling or her not. Turning their little game with his fetish into a full-time thing.