If you're looking for manga similar to 3 Gatsu no Lion, you might like these titles. All recommendations are made by Anime-Planet users like you!
Both stories are about kids who enter the world of professional shogi playing. Both main characters need shogi to be able to deal with their lives. They also share topics such as friendship, complicated/tragic family situations and a general coming of age theme. If you like one of the two you would probably enjoy the other too.