Mortal Shell 2 multiplayer is not supported by the supplied store materials. Steam lists the feature as Single-player, while PlayStation Store lists offline play enabled and 1 player. A collected Steam Community source also states no multiplayer or co-op features are in development or planned.
Store Listings
Steam’s official store material gives Single-player as the feature. PlayStation Store similarly describes offline play enabled and 1 player. These two store entries are the strongest sourced answer for the player question.
Community Statement
The collected Steam Community material says there are no multiplayer or coop features in development or planned for Mortal Shell II. This supports the same practical answer as the store pages. Any later roadmap change would need a new official source and is 待确认.
What Remains Unknown
The materials do not describe asynchronous messages, invasions, cross-play, shared progression or online leaderboards. They also do not confirm a future expansion that adds co-op. Treat multiplayer claims outside these sources as 待确认.