While checking to see if DsDsRevolution had been updated i found another Japanese blog with a homebrew i haven't seen before, Lost Cities DS by tambourine_dc. Lost Cities is a card battler game in which you can use a Mii avatar, you can create those here. It's based off a card game of the same name by Rainer Knizia. The release is from back in February, but seeing as no homebrew sites have posted it apart from a few Japanese blogs (or so google search tells me), i thought i would up it here in the hope that it might gain a bit more notice from the scene.
http://yaplog.jp/tambourine_dc/archive/229