Former K-pop idols Thunder of boy band MBLAQ and Mimi of girl group gugudan revealed that they have been in a romantic relationship for the last four years.

“I revealed my relationship with Mimi through ‘Second House,’” Thunder, whose real name is Park Sang-hyun, said in a handwritten letter on Instagram on Friday.

“We hope you support our relationship ... I also would like to send a message of gratitude to the fans who have supported us. I will be presenting a positive side of myself as a passionate artist,” he added.

Mimi, whose real name is Jeong Mi-mi, also shared a handwritten message on her Instagram.

“I wanted to share the news with you personally, but I have had to share the news through the broadcast,” she wrote.

“I have someone who I wish to spend my entire life with,” she said. “I hope you support our future with warm looks.”

A trailer for KBS’s variety show “Second House 2” released Thursday showed Mimi and Thunder meeting with Choi Soo-jong and Ha hee-ra, one of the most popular celebrities couples in Korea and sharing that they have been in love for the past four years.

Media outlets reported the same day that the couple will tie the knot late next year.

Mimi debuted as a member of gugudan in 2016, known for songs “Chococo” (2017) and “Not That Type” (2018). The group remained inactive since 2019 but officially disbanded on Dec. 31, 2020.

Mimi did not sign with an entertainment agency since her contract expired with Jellyfish Entertainment but is continuing her career as an actor.

Thunder debuted in 2009 as a member of MBLAQ. He left the band in 2014 and has released multiple solo albums since. Thunder also kicked off his career as a rapper last year, releasing his first hip-hop single, “Up.”

BY CHO YONG-JUN [cho.yongjun1@joongang.co.kr]