Piling up the Dolls of Fate

A story about Uika and Mutsumi revolving around Sakiko.
A distorted love triangle shines wildly on the stage.

Uika and Mutsumi are set to perform a new solo piece.
Uika, eager to have Sakiko’s attention all to herself, makes a proposal to Mutsumi.

"Give me your solo, Mutsumi-chan."
"I don't understand what you're saying, Uika."

Who, in the end, holds the strings that manipulate these dolls?