Adrianna Tan@sashin people have used it to achieve a fairly high level of speaking and understanding. it's probably the best thing you can do on your own without going into an intensive immersion program.
GNU social JP is a social network, courtesy of GNU social JP管理人. It runs on GNU social, version 2.0.2-dev, available under the GNU Affero General Public License.
All GNU social JP content and data are available under the Creative Commons Attribution 3.0 license.