Hello fellow members!
I came across two Nintendo DS development cartridges through somebody living in Japan. Both of them appeared to hold prototype builds of unreleased titles that were developed by A-Max in 2007-2008. I personally believe that these two prototypes were supposed to end up in a single game judging by the sports genre and similarity between both games. They are both very similar, including featureless character models along with two buttons saying "HEAD" and "BODY" which are being displayed on the bottom screen. Using the head and body buttons during the boxing game simply dodges incoming punches whilst B performs an uppercut, A performs a jab, Y performs a jab with the opposite arm and X performs a hook. In Tennis, only the A button is used to hit an incoming ball and the bottom screen moves the player towards the NPC and back to their own side of the court. I believe both of these were made with the touch screen in mind and having the other buttons serve as alternate controls and plays much better on a real DS system. I also contributed them to the main site itself here and here. Thanks for reading!