J-crosswords by renshuu is an Android-based game that helps you learn Japanese words while enjoying Japanese crosswords. Developed by renshuu.org, the game is free to use and doesn't have any advertisements, timers, or stamina system.

The game provides over 9,000 Japanese words categorized from beginner (JLPT N5) to advanced (JLPT N1), with over 300 free puzzles and over 1,500 more for paid users. It also offers lists for popular Japanese textbooks like Genki, Tobira, and Minna.

J-crosswords by renshuu offers two ways to play, keyboard input, and drag and drop for keyboard-free play. The game is available in English, German, French, Dutch, and Spanish, making it accessible to people around the world. You can also track how many words you have used in each category with the help of vocabulary lists. Plus, you can unlock hand-drawn scenes from Japan as you solve puzzles.

Overall, J-crosswords by renshuu is an excellent game for anyone who wants to learn Japanese words while enjoying Japanese crosswords. It is easy to use, informative, and entertaining, making it a must-try for anyone interested in learning the Japanese language.