The secret of "Aimo", the lullaby that only Ranka and Brera know is finally revealed.

Due to repeated Vajra attacks, the Frontier colonial fleet's resources are shortened. Energy becomes limited, and water and food rationing increases the population's unease.

In the on-going war against the Vajra, people lose their loved ones and their hatred grows. Refusing to be a singing tool and wanting to clear up other people's thoughts, Ranka is determined to take a major step.