The new Mario & Sonic game will include 14 sports via Olympic & extra events and 40 characters (and also Miis) in total. The 3DS version will include local multiplayer, download play, online leaderboards, Amiibo support, and street pass.
The game also has a story mode and a brand new Outing Marathon mode, which uses the 3DS pedometer to count the player’s real life steps with a walking goal of 42.195km. Check out this article for more information about Mario & Sonic at the Rio 2016 Olympic Games.
And here are two new videos featuring footage from the Japanese version of the game:
Are you looking forward to Mario & Sonic at the Rio 2016 Olympic Games?
Sources: Nintendo Everything articles here and here