This has actually been out in English before. I used to play it. It certainly wasn't originally launched yesterday - re-launched, maybe, but it's been running for a while now.
Here's the site, since Joshex didn't link it.
Personally? I found DMO to be horrendously limited for a 'free' game. A lot of features are basically only available through items sold in the cash shop. The fact that these are tradeable by players doesn't help much, because people ask for exorbitant amounts of money for them.
There's also no character customization. You can't make an entirely original player character - you're limited to choosing one of the 3 main heroes of Season 5: Data Squad - Marcus, Thomas, or Yoshino, and either Agumon, Gaomon, or Lalamon as a starter Digimon. You're not limited to the canonical digimon of each character (you could play Yoshino with Agumon as a starter), but that's the only customization you've got.
Finally, there are a LOT of grindy mechanics in this game. Got a digi-egg? Congrats - now good luck getting the data to hatch it. Oh, what's that? It's a poor-quality egg? Sucks to be you, go grind a better one. What? The egg broke when you tried to fill it with data and hatch it? Sucks to be you, go grind a replacement. What's that, you had a cash-shop egg, and used the best-quality data to hatch it, and it still wound up having crappy potential? HA HA HA, SUCKS TO BE YOU.
Honestly, after about two weeks of struggling with it, I figured I had better ways to spend my time.