Shio no Machi: Jietai Sanbusaku Series

Synopsis

The era of "salt damage" when salt fills the city. Mana, who lives in Tokyo which is on the verge of collapse, picks up a weakened young man carrying a heavy backpack named Ryouichi. Together with Akiba, a man who acts like her guardian, the three head towards Ryouichi's destination, the sea, but...? (Source: Hakusensha, translated)