The third and final installment of the Neptune OVA Series Trilogy. 
Magiquone, with her secret plan against the goddesses, Level Trick, appear to challenge the battle. While their guard are down, Level Trick's "Level-Down" attack hit the four goddesses. But Magiquone is also caught up in the aftermath. Worried about their sisters' disappearance, Nepgear and the others go out to search for them, and found Noir and the other sisters, who had been transformed into young children as a result of the Level Down attack..., and only Neptune is still missing. 

 Meanwhile, Magiquone and Neptune are running a vast eggplant farm. They, too, have been transformed into their younger form and lost their memories due to the effects of Level-Down. What will become of their strange shared life with their eternal nemesis...? 

(Source: Crunchyroll) 

Note: The OVA had an advance release on various streaming platforms in Japan, July 2022.

Choujigen Game Neptune THE ANIMATION: Hidamari no Little Purple