To answer Jake H Vorok's question Blake is still in Remnant protecting Atlas and Mantle.
Luz and Kim were at the park looking around. "Man Kim the nature in the demon realm is amazing." Luz said. Suddenly a portal opens and Star and Hanazuki came out as it closes. "Who are you?" Luz asked. "I'm Star and this is my adopted sister Hanazuki." Star said.
At the castle Star and Hanazuki were in the throne room. "So princess Star and Hanazuki what brings you here?" Alexander asked. "Well we were sent by our mother queen Moon to help a little project called 'project unification'" Star said. "Oh that my project. See after witnessing Harmonic Convergence I thought it would be a cool idea to unite the different realms. I did sent the invitations to another realm." Luz said as a portal opened and Unikitty and dr.Fox came out as it closes. "Hiii! I'm princess Unikitty of the unikingdom and I got this invite to a project unification." Unikitty said. "Welcome I'm princess Luz and I'll be your host now let me show you all around." Luz said as she and the visiting royals went to the other rooms.
Meanwhile two mysterious figures look around and saw the castle.