Some elements of this episode were based on the sidestory Casablanca Memory, which appeared in volume 11 of the original release of the manga. Despite when it was published, it takes place during the early Dark Kingdom arc, after Jadeite is killed in Act 3 but before Zoisite is killed in Act 7. Casablanca Memory was never adapted into the anime in any way (which makes sense given that Rei is such a different character in the anime).

Although it is clear that this episode had a basis in Casablanca Memory, the two actually have very little in common. In both, Makoto and Rei become more familiar with one another. Also, both share details of Rei's relationship with her father - he is a politician, and his political career always came above his family, which means that he didn't come home very much. Rei hates her father. The fact that Rei's mother died when she was young is also brought up in both.

However, some specifics of Rei's relationship with her father were changed. In the manga, Rei chose to live with her grandfather at the Hikawa Shrine after her mother died because she didn't want to live her father. In PGSM, he gave her to the shrine to take care of her because he hated Rei's powers. In the manga, it seems that Rei only sees her father when they have dinner on her birthday (and even that doesn't always happen), whereas in PGSM they meet once a month for lunch. The specific fact that Rei's father did not come home even when her mother was dying did not come from the manga. In general, although Rei's father does not appear in this PGSM episode, he is a much more active presence than he was in Casablanca Memory. The meeting in this episode was for the sake of her father's image, and the fact that Rei escapes is an aspect of character development that the manga never hinted at.

Possibly even more significant is that Kaidou is not present or even mentioned in this episode of PGSM, and it can be presumed that in the PGSM universe he does not exist. Rei's relationship with Kaidou was something of a tragic romance. This is part of what led to Rei's distrust of men. In general, this episode did not create any link between Rei's past and her lack of interest in men. (However, Act 4 of PGSM did seem to link Rei's past to her general reluctance to trust others, which we can presume was done with this episode in mind.)

The rest of Casablanca Memory's plot was simply not used in PGSM. It involved Zoisite using music boxes to create an eternal rain based on people's sad memories, which would then steal people's energy. He was doing this partly to get revenge on Sailor Mars for killing Jadeite. It might be that Zoisite helping Jadeite in this episode of PGSM was a nod to that.

Pretty much everything else in the episode was original to PGSM.