WARNING: This article contains spoilers. Please read at your own risk!
In order to return to their world, Souseiseki, who was brought back to life thanks to her sister’s sacrifice, convinced Suigintou to return the Rosa Mystica to their rightful owners. Suigintou agreed, which in turn allowed Suiseiseki to come back to life. Together, they managed to restore order to both worlds.
Cute cosplayer! I guess Suiseiseki is still really popular, given that she is the “desu girl”. Thanks again to Fumiki for sending this in!