It was serialized in Kodansha's Weekly Young Magazine from July 2014 to June 2019, with its chapters collected in nineteen tankōbon volumes.

Koharu finds that her boyfriend was a married man, who was cheating on his wife with her, and was the third guy to do so in a row.

Desolate, Koharu decides to leave Tokyo and move back home, rejecting a future of love and marriage for simpler life.

Koharu learns that her hometown has legalized polygamous marriages to counter declining birth rates and becomes Ryunosuke's third wife.

Written and illustrated by NON [ja], Harem Marriage was serialized in Kodansha's Weekly Young Magazine from July 23, 2014, to June 17, 2019.