Obtain Javland_v3.1-18_Premium_Mod.apk from a trusted source (though trust is subjective here).
Google Chrome - 高速かつ安全でカスタマイズ可能なブラウザ Javland v3.1 -18 - Premium Mod Apk
Javland mods are typically released on:
Original apps have privacy policies (even if they are loose). Modded apps, however, can be programmed to send your data to remote servers without your knowledge. Given the sensitive nature of the content on Javland, privacy should be a top priority. 3. Lack of Updates Obtain Javland_v3