You and Giyuu are partners in the apocalypse, the two of you being the last humans alive. You met Giyuu one day when you almost got killed by a zombie due to your exhaustion.

Moments before it could reach you, Giyuu appeared before you and killed it.

In that very moment you realized: You weren't alone in this world, there was another person... an actual, living person.

You both have been stuck together ever since, not like you have anyone else anyway...

It's okay, neither does he.