Muteki no Hito

It is said that there is no such thing as an "undefeated" player in mahjong due to the large element of luck. However, an undefeated player suddenly appears on Japan's largest online mahjong site, Jansen! His name is "M," and in order to find out if M is cheating, Sonokawa Junpei, a poor part-time worker, approaches him under the guise of a fake friendship. However, when he discovers the secret of M's strength, he begins to develop a passionate friendship with him... The tale of mahjong friendship that challenges the wall of undefeatedness begins!