Plan for a solo campaign
The current Steam product information lists single-player and does not advertise co-op or competitive multiplayer. Do not buy a second copy expecting a shared campaign on the strength of an unofficial multiplayer tag or an old series memory.
Cloud saves, controller support and Family Sharing are separate storefront features. None turns a one-player game into simultaneous co-op. Likewise, being sold on several platforms does not imply crossplay.
Why two September dates appear
Capcom Town’s release update moved the game from September 25 to September 4, 2026. Older June announcement pages still carry the superseded date. Steam’s regional record displays September 3, while the global publisher messaging uses September 4.
On September 5, the Steam app is released rather than upcoming. When checking availability, trust the current purchase or install state and a dated publisher update over a cached preorder headline.
What to check before organizing a session
If your goal is playing together, ask whether you want simultaneous characters in one game or simply to compare progress while each person plays alone. Onimusha supports the latter as a social arrangement, not as an advertised in-game multiplayer mode.
This answer is a dated feature-list check. We have not found an official future co-op announcement in the reviewed material, and we will not turn that absence into a claim that the developers can never add one.