The Idolmancer Game Over is an ending which occurs when the player loses to the MC: Yurimancer.
Sensing that the Mistress is preparing something huge, she instead comments that the two aren't bad at all, before sending Yue and Mai to possess Eric(a) and Yoshida, respectively. She reveals that the two spirits were rather successful idols when they were alive, and also her most loyal supporters. She has been looking for new vessels for them for quite some time, however since their spirits become stronger with each day it's hard to find a vessel strong enough to handle them, until the two Magical Girls came along. Despite the initial reistance, the Mistress seals their souls away inside their own body, leaving Yue and Mai to have full control.
Yue decides to shrink Eric(a)'s body in order to look much cuter, however this process momentarily leaves her exhausted, though she quickly recovers thanks to Mai's encouragement. As for Mai, she decides to keep her host's sporty look (albeit with a slight change in bust size) as she wants to be little Yue's protector. As a finishing touch, the Mistress gives them new clothes more fitting for an idol, which she designed from her brief study about fashion. The girls are so overjoyed that they even take off their new clothes and make out on the street for several hours, before falling asleep in bed together.
In the days that follow, Yue and Mai brushes up their performances to restart their idol carrer, while Eric(a) and Yoshida furiously tries to reclaim their control, but the seal prevents that every time. Eventually their spirits are so weak that the idols were able to repel them without the seal's help, meaning that they are now disconnected spirits. Soon Eric(a) feels more distant from now Yue's body, and their anger at first now becomes encouragement. Yue explains that now that Eric(a) is a lost spirit wandering around a necromancer like her, they will be influenced to be more like her, and somehow Eric(a) feels content with the answer, knowing that Yue has been using their body better than them.
Eventually, when Eric(a) can be temporarily released outside, they meet up with Yoshida, and the two of them feels happy that Yue and Mai took over. When they're able to fully manifest, they're even hired as the idol-mancer's backup singers and dancers - Eric(a) even get a small cult following of cult members. By this point, the cult has taken over the world, creating a new civilization from zombies having lots of sapphic sex together. The only step forward is to take the idol fever interdimensional - and so, with Yue and Mai spearheading the yuri zombie invasion, Eric(a) and Yoshida now assist the idols in hosting massive concerts and turn every last inabitant into part of the lesbian undead orgy.