Is Echoes of Aincrad multiplayer or single-player only? The "10,000 players" premise is confusing me

Echoes of Aincrad drops July 10 and I'm trying to figure out what it actually is before pre-ordering.

The premise is being one of 10,000 players trapped in the SAO death game, so I assumed some form of online play. But the official Bandai Namco FAQ says there's no multiplayer mode — you get an "autonomous partner character" instead. Meanwhile the trailers show party gameplay with Argo, Kirito, and Asuna, which looks like co-op at a glance.

So is the entire game solo with AI companions? And if it's fully single-player, does it need an internet connection beyond the Denuvo activation?

Planning to buy two copies to play with a friend — no point if there's zero co-op.