This short story manga was first published in the back of the Sailor Moon Materials Collection and later collected in the Sailor Moon shinsoban edition “Short Stories Vol. 2” (available in English individually and in the Sailor Moon Box Set #2).
The out-of-continuity story is set in an imaginary alternate (or “parallel”) timeline in which Usagi has a second daughter after Chibiusa (Takeuchi Naoko has stated clearly that Usagi will only ever have the one daughter in the canon story). Her second daughter’s name is Tsukino Kousagi, and she is “Parallel Sailormoon”. The characters on the first page are the inner senshi grown up. The young versions of Makoto, Minako, Rei and Ami that you see in the bottom panel on the second page (back of their heads) are their lookalike daughters.