Mari Yaguchi will be getting married on March 26, media outlet Nikkan Sports is reporting.
Yaguchi, 35, will be marrying a 30-year-old former model. The two have been in a relationship for 4 years.
News of Yaguchi's impending marriage was first published by Sponichi yesterday.
According to officials from Yaguchi's office, the couple has spent the year preparing to get married, and reported their intentions to the agency.
The identity of Yaguchi's future husband has not been officially revealed. However, it is widely believed that he is Kenzo Umeda, the man she was caught having an affair with during her first marriage with Masaya Nakamura.
There are no plans for a wedding scheduled at this time.
Yaguchi's relationships have been of particular interest since her time with Morning Musume. The idol was caught dating actor Shun Oguri in 2005, causing her to withdraw from the group for betraying her position as an idol.