Hare-Kon.

The man Koharu loved wasn't cheating on her...he was cheating on his wife with her! And not only that...he was the third guy in a row to do so. Dejected, she leaves Tokyo for her hometown, and rejects a future of love and marriage for a simpler life. But things have changed—her parents are struggling, the café they ran is closed, and a creepy man keeps following her around. She thinks this may be it for her, until she learns that her hometown has allowed polygamous marriage, and she's in that man's sights as his third wife!

(Source: Kodansha USA)