Chito and Yuuri have arrived at the highest stratum, but their journey will not be over until they reach the very top of the city. Along the way, they continue to explore the evidences of humanity's innovation and growth through the ages, now nothing more than crumbling ruins. Having learned what th...

Chito and Yuuri have arrived at the highest stratum, but their journey will not be over until they reach the very top of the city. Along the way, they continue to explore the evidences of humanity's innovation and growth through the ages, now nothing more than crumbling ruins. Having learned what they can about the past, what awaits them in the future as the girls embark on the final leg of their tour...?