I wanted to bump this thread before to thank the translator and to bring more attention to it, as I think this is a pretty cool game. I got distracted with other stuff and haven't finished playing it yet, but this game is definitely playable on melonDS (at least up to chapter 11 out of ~18). I think it would run on DeSmuME as well, but I found it a little less efficient on my old laptop. I used the
patch linked a few messages up and I haven't encountered any bugs yet.
This game has full Japanese voice acting (on DS!), two story routes, rich and diverse character cast, nice artwork and pixelart and enjoyable turn-based combat. There are also support conversations with a chosen character after each chapter that will let you unlock some powerful joint moves, if your relationship level is high enough (similar as in Luminous Arc series).
What's important is that you don't have to be a fan of the Summon Night series to enjoy this game as it is self-contained. This is the first SN game I ever tried and I knew nothing about the franchise. Playing it convinced me to check the other entries in this series in the future.
The only problem I have with this game is that it seems to be aimed at a little younger demographic (teenagers let's say), so I think some story elements might have been made a little more dramatic to add greater impact on mature audience.
But I recommend checking it out for yourself.
I wish the intro/opening of the game was uploaded somewhere in higher quality, as I think it really sells the game: