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As a Monk he should have been fearless, and willing to help people.
At some point, he took Guko under his wing and became Guko's teacher. He was friends with the Guardian Deity, and one day went into the woods to fight a monster.
Little did he know that monster would end Koshin's life, and steal his clothes. Guko avenged Koshin's death, and killed the Hitokui.