Sumire and the others were able to get home from the tragic incident on Venus. Their new alien friend, Ian Lavishine is with them and stayed in Earth for awhile. He won't be going back not until he finds a way to save his planet. The other planets heard of the incident as well and placed high security in all primary PriParas to protect the PriPara Crest.
The PriPara Crest is what binds the planet's PriParas together. Like how in Earth there are many different kinds of PriParas, the other planets have a variety too and the main headquarters holds the PriPara Crest. The twin aliens seem have to something planned for taking the crests, not only their target is Venus but the others as well.
However, before we get into the deepest detail, we'll tackle the events on planet Earth. While the others lead by Zwolympia are in Venus saving Sumire, Ichigo, Yurika and Nozomi, the man that showed up earlier before this happened seems to be lurking around the city, in search of something.
Ayumu: Let's see here! This place sure hides many secrets. I wonder if that young woman said about the Fountain of Youth is even real.
Just then, Akane happens to be in the same area. Busy with her research and with Galileo gone, she has Layla accompany her. Mikan in her PriPara form and Ann as well.
Akane: I've radiated high detections of strong, paranormal energy around the area. My curiosity has reached it's peak and I'll find the ultimate source of this.
Layla: You don't have to, Akane!
Your character spotted the four girls. Seeing their crazy instruments, you can't help but grow curious of their activity and approached them.
Ann: Ah, Sky! Just accompanying her for she needed some help carrying these...heavy instruments.
Akane: DO NOT TOUCH ANY OF THESE INSTRUMENTS! They're fragile, expensive and can cause serious damages if not handled with care. *her device radiates even more* Oh shh...Listen! Something strange is going on in that cave.
Layla: Do you want to come. We may need many witnesses. xD