Responses
I think it is the story of the other characters, and probably will avance further than the beggining of the other one.
In fact I just checked and the main character of the other story appears on the second page.
The story starts in present day and goes 1.5 years in past where Takemoto and his friend, Watamori, walked in the bar. The story we are reading is 1.5 years in past from the other manga.
I think this is the prequel of that one, since Makoto/Akihiko are still sex friends and Toma/Take are just starting to date here they are an established couple in that one. Also MC of first hasn't joined them yet.