Satoru Iwata has announced the Mario Tennis Open release date during his Nintendo Direct broadcast this morning. Mario Tennis Open will be released for 3DS in Japan on 24th May.
In more news, Iwata also revealed that Mario Tennis Open can be played with the buttons or the touchscreen and it will also utilise gyro controls.
You'll be able to play online or have a local game with three friends.
Best of all, you'll be able to play as your Mii in Mario Tennis Open.
You can Watch Nintendo Direct live here.

This is good news. A new multi-player game for 3DS will go down well, especially if they're planning on releasing this before Christmas for US and EU.
as i was watching i changed my mind about this game. it may very well be quite good...
Good to see more of this game! I love that your Mii will be customisable.
If anybody at Nintendo UK has a brain (and to be fair, a few of them seem to be growing them over the last year or two) then a June 22nd release date is a must. Why? Three days later Wimbledon starts. Perfect timing. Plus I don't want to wait too long either. Make it so.
This is fantastic news,I can't wait for this game.