About the Snowball Earth Manga Volume 1

Yukio was destroyed in battle and Tetsuo survived in an escape pod. After eight years in cold sleep, the escape pod finally lands back on Earth, and Tetsuo awakens, determined to fulfill his promise to his comrade in arms that he would live his life to the fullest and make many friends. But what he finds instead is a world in ruins, entirely frozen beneath a blanket of ice and snow-a snowball Earth! What happened to humanity, how did the Earth freeze over, and will Tetsuo be able to keep his last promise to Yukio?