Oh lol I was wrong about the sword & him. He's still the side-main character, not the chosen Hero.
@ThaTruth0218 It's not wrong at all to look at your life mentor as the strongest being alive (instead of his father, as an example). Why not your best person instead of an undefeatable archenemy? It's because the Old Man was & is his greatest admiration, highly regarded, & the closest person that shaped him to be who he was at the peak of his life while the world's crisis was at the worst. It's not plot, it's who you prefer to look up to from the feeling of your heart. & along that line of thought, why would you even look up to your enemy who'd kill you in a heartbeat? & he doesn't have fear toward the strongest being he knew (like the demon lord he couldn't even face upfront), thus his Old Man was the choice his heart made to face in the trial.
TlDr: He only has the highest regards, admiration & deepest remembrance for the one being strong enough to personally shape him to also be strong to face the impossible in the future. & fear (toward the demon lord as a strong being) isn't what controls him to influence that test.