Can also be considering the mc as a sponsor for a motive or fun. preferably unique weapons but any is fine.
Sorry, but i can only recommend this I Am an Evil Sword. Mc is a sword and he will be in hand heroes and villains alike.
Maybe something like: Kajiya de Hajimeru Isekai Slow Life Spoiler At least the opening part of 1st chapter show how a fight between a hero & a demon lord came to a stalemate, only 'coz the weapons they used came from the same blacksmith (MC) The New Gate Spoiler MC's 2nd job is blacksmith & he makes/upgrade some weapons mostly for his friends & followers, though some of them do fall to the enemy's hand