Not the admin, the character.
I noticed this my second time through, but it's pretty heavily implied he knows Akira and co are the Phantom Thieves, as early as when he starts the site.
His texts and Akira's blatant choices in answering also confirm it's him accomplishing the requests.
And any 'speak to them for me, k?" Is for public talk. A wink-wink between them.
Despite that, much later in the game Mishima will either send a text or naively say "Tell the thieves this for me!" Or something like that. I wish I screencapped it, but it was at least midway through. And I remember being like HUH?
There's no way he's actually this gullible, or was it more posterity?
Discuss.