M.League is a Japanese/Riichi Mahjong team competition in Japan. Ten teams of four players each compete in a 120-game regular season. The top six scoring teams at the end of the season qualify for the semifinal round of 20 games, for which half of their team's score from the regular season is carried over. The top four teams at the end of the semifinal round qualify for the final round of 16 games, for which again, half of their team's score from the semifinal round is carried over. The team with the highest score at the end of the final round is the overall winner.

Official M.League site (Japanese): https://m-league.jp/
Official M.League Twitter feed: https://twitter.com/m_league_
English-language blog that provides information and updates on the league: https://mleaguewatch.wordpress.com/