Choujigen Game Neptune The Animation OVA

Neptune and the other goddesses reunite with their younger sisters at a mountain resort in Lastation, planning a quiet summer vacation filled with hot springs and relaxation. The peace ends when Nepgear, Uni, Rom, and Ram wander into the mountains and pass through a long line of shrine gates, only to find themselves suddenly transported into a parallel dimension.

Separated from their sisters, the girls search for a way home until Nepgear encounters a woman who looks shockingly like Neptune, only older and more mature. What first seems like a reassuring familiar face opens the door to an alternate world unlike the Gamindustri they know, turning the vacation into an adventure through versions and memories they never expected to meet.