Fyi, in Korean, 동지(Dong-ji) has several meanings

1. 동지(同志): (=friends, companion) People who share the same values, interest, viewpoints etc

This is what Moonbyul wrote in the poster, as you see, so I guess she refers Moomoo as her 'friends'

@RBW_MAMAMOO

But she also wrote "The night is long, so our story goes on."

so we can guess she use "Dong-ji" with another meaning too.

2. 동지(冬至): Korean traditional day that celebrates the longest night of the year.

The following is the article about Dongji

https://www.korea4expats.com/article-dongji-winter-solstice.html

Fun fact:

Moonbyul was born in Dong-ji(Dec 22nd), the winter solstice, which has the longest night of the year

And Hwasa was born in Dae-Seo(July 23rd), the hotteset day of the year

@RBW_MAMAMOO