三番目の月

Sanbanme no Tsuki

There is a planet where all the inhabitants have mysteriously disappeared. This planet was called "Earth." Four people—Shiki, Miyuki, Yoshimura, and Satou—are dispatched to investigate the planet, its remaining living things, and the remains of the culture that once thrived there. Together, they pass peaceful days on the quiet Earth. (Source: MangaHelpers)