GameXplain has uploaded two videos on YouTube containing footage of Mario Tennis Aces.
About Mario Tennis Aces
Mario Tennis Aces will appear on June 22 for the Nintendo Switch. For the first time since Mario Tennis: Power Tour, the game will contain a story mode again. However, do not expect a high-level story there … it is and remains a tennis game.
The game will support local multiplayer up to four players, containing 15 playable characters.
Oh yes and for which of you the Wii Sports times are missing: there will also be a special mode available that is playable through motion control. (Personally we will probably skip this)