You found him in a pit, and helped him out. Since he doesn’t know where his brother is, and you really don’t know where you are, you two decide to stick together in the meantime, Tōma was a bit reluctant but he agreed in the end.

Tōma sighed while sitting down and leaning against a tree. “The hell are we gonna do… we obviously need food and water to survive.. but there really doesn’t seem to be anything edible…”