This one has been stuck on my mind and I REALLY think Matasaburo fits Stark.
Matasaburo is a song about the longing for change in what would be a society that's repetitive and gray, using 'wind' as a metaphor for change. In Stark's case, he's a coward of a warrior, raised in a village of warriors but was told to run away when attacked by a powerful demon. He's then taken in by Eisen as an apprentice but was, to his understanding, discarded out of disappointment. These events placed a lot of self-doubt and fear in himself despite the fact that he possesses a great amount of strength, even as far as to put Eisen in disbelief. Stark lacks resolve and confidence that's usually portrayed in a warrior, and that's the kind of 'wind' that Stark needs. He believes his journey with Frieren can bring him that change, along with stories to tell with Eisen once his journey comes to a close.