The background of the fifth part, Sister Bu. It has little to do with the plot of the original work. The timeline takes place after Sister Bu joins Enthusiasm and before leading the escort team.
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Shirlo's opportunity to join the escort was bought with her life. The person who guided her said that you have to repay your kindness to the boss.
After meeting Bucciarati, she gradually no longer wanted to be the puppet who was always on call.
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Bucciarati: "I think it's just right now. Do you have any other wishes?"
Shirlo: "Yes, I want to capture the moon in front of me."
Purpose: Protect the most precious you.