Sekai (World) is a mysterious world seperate from the real world where VIRTUAL SINGERs can live.
There are different Sekai worlds, each one answering the wishes the of creators who want to turn their feelings into songs. The feelings of a person are put in physical form inside the Sekai. VIRTUAL SINGERs live and appear in these worlds, with different appearances in each Sekai. They help people discover their true feelings.
People can travel to Sekai using "Untitled" songs. These songs have no melody or song and are created at the same time as the Sekai. Playing an "Untitled" song will transport the listener to the Sekai.
- As mentioned in a area conversation, if a member's phone battery dies, they will be forced kicked out from the Sekai and go back to the normal world.