Found this on the stage48 forum:

Hamamatsu Riona

Current lineup

1media group.jpg

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Google translated:
''Japan-Korea girls k-pop group "Z Dream Z" will debut in Korea at the end of June 2021 ❗️ The Japanese-Korean girls k-pop group "Z Dream Z", which was born at the audition last year, will finally make its debut in Korea at the end of June 2021. Digital single & PV simultaneous release! Debuted in Korean media! !! Details will be announced on our website and SNS. In addition, we will release information about members as soon as the information is lifted. Please look forward to it. The video is practiced by the members of "Z Dream Z" with the songs of the K-POP group produced by No1 Media.''

Japan-Korea Girls K-Pop Group NEW GIRLS GROUP G (tentative name) will make a major debut in Korea in June 2021.

This group is a joint unit of selected members of No.1 Media JAPAN who passed the Mikucha distribution audition held in 2020 and members of Korea's No.1 Media led by CEO Jun Kang.

The purpose of this audition is to recruit Japanese members of the girls unit who are scheduled to debut in Korea from their debut in Japan.

The members who passed the Mikucha distribution audition were sent to Korea in 2020, and they were planning to make their debut in Korea within the same year, but the spread of the new coronavirus that involved the world forced the project to stop.

However, participation in the Korean debut program and steady work to improve skills continued under the hood, and I was able to send some members to Korea.

Currently, they have firmly participated in the debut program and have come to the point where they can make their Korean debut in June 2021.

Even so, the next girls K-pop group's Korean audition will start with Korea's No. 1 Media, and recruitment will start in Japan at that timing.

https://no-1media.jp/audition/

Source: Stage48.forum

Quote from bartkun

wait that's interesting just don't get last line because at one point they say that group will debut in june but then they say that Korean audition and recruitment in Japan will start in same time...

so what they want to like debut sub-unit, or not full group?

I'm confused myself. The song they covered is Lipbubble - Yellow Pink and they used to belong to Zenith Media Contents. After reading the stage48 post, it seems this is the same people behind LipBubble and Zpop.