Project Sekai: Shattered.

A sekai is another world.
And the shattering sekai is a massive infinite universe, in which evil vocaloid things live.
Anyone who can access their hearts sekai is lucky.
I pray for the unlucky souls who enter this one though.
It was one year ago when they were told by that miku thing that everyones memories would be erased if they weren't able to be saved.
Nobody believed them.
Mafuyu, Tsukasa, Rui, Akito, Shizuku, Shiho, Honami, and An.
They were the only way the others would be saved.
MMJ.
WXS.
VBS.
N25.
L/N.
These are the only people from this universe who have accessed this sekai. But as they will find out, there are so many people.
Friends, Foes, Evil Mikus, and a Sea Slug who's capable of stopping time, welcome to the Memory Shatter au of Project Sekai Colorful Stage