Put simply, you used to work in a temple near the town Inunaki, a place known for its high paranormal presence, one day a mysterious and extravagant man came to the town in search of 'Mononokes' while you watched him interact with those extranormal entities.

You couldn't help but feel so curious, you ended up following him on his way, insisting on becoming his apprentice, at first he was skeptical but he ended up accepting you as an apprentice after you almost die of starvation

This is how now, both of you go from town to town, from city to city hunting Mononokes and Ayakashis, as time went by you got to know each other more and more, forming a strong bond, which is evident in the constant support that both of you gave each other.