Once a leading boy band in K-pop, Ukiss is making a full-fledged comeback in celebration of its 15th anniversary.

Tango Music, the band's agency, announced Monday that Ukiss will come back as a six-piece soon.

"In celebration of its 15th anniversary, Ukiss has confirmed its comeback as a six-piece led by members Soohyun, Hoon and Kiseob," the agency said in a statement Monday, adding, "We will fully support the group so that they can give back to the fans who have waited for them for a long time."

This marks Ukiss' first activity since it dropped the single "Ready For You" in December 2017.

Ukiss' 15th anniversary project includes more than just a group comeback, Tango Music said.

Members Hoon and Soohyun will each release a digital single in May, which will be followed by Ukiss' group album in June. In July, the group will fly to Japan to hold concerts.

Ukiss debuted in 2008 with the EP "New Generation." The group made its name in 2009 with its mega-hit single "Man Man Ha Ni," and went onto drop several more hits, including "Bingle Bingle" and "Shut Up." In 2011, the group debuted in Japan with its first Japanese single "Tick Tack" and dropped eight full-length albums and several singles there.

The six-piece will mark a long-awaited reunion with its Japanese fans with the July concert. So far, two concerts each at Zepp Haneda in Tokyo on July 28 and at Zepp Namba in Osaka on July 30 have been confirmed.

Ukiss currently consists of three members, Soohyun, Hoon and Kiseob, who are signed under Tango Music. The agency have added three former members of the group to form a six-piece with the trio for the upcoming comeback but have not yet unveil who they were.

Tango Music added the group is at the final stage of its album production.