As we come back to the present time we see our protagonist, alone,walking.
We can't see his whole body because he is covered with Sensei's robes.
But we can see a little tiny glowy thing, floating near him.
He looks at the thingy and says "Hey Cinnabar, do you know what a song is?"
"The professor told me that is something you do with your voice and you do it when you want to make someone you love happy"
Our protagonist starts to hum with his voice, trying to copy the sounds of instruments, then he starts to sing in the emptiness of the island.
"Fly me to the moon...and let me play among the starts...."
As he sings the song, he notices that the other gems are also singing...Cinnabar,Antarc,Ghost,Dia,Cairngorm,Sensei...
As the other sing with him, our protagonist starts to secrete some kind of shiny dust from his eyes.
"In other words" our protagonist starts to scream as he reaches the end of his trip and the end of the song.
"I love you..." As those words are pronunced our protagonist turns quickly, for him to see a mysterious figure,
shiny and white, our protagonist knew what type of gem that was, it was a pearl.
Both of them start to sing the song again together with everyone else, and them they did that again and again and again...
That's the true houseki no kuni, the true land of the lustrous.