I believe it is: rationality.
Explanation:
What is the main problem in this story? The miller needs a job and worries about people's opinion of him.
The Noh drama's main character must resolve his Inner conflict.
Brutus' tragic flaw of idealism contributes to his downfall because he was gullible enough to be convinced by Cassius and Antony that they were going to murder Julius Caesar for Rome's development and goodwill. He was blinded by that idealism and believed that these were their true intentions for inviting him in the murder, thus, making him involved greatly and made him feel guilty - leading him to suicide.
Readers learn the narrators own analysis and explanation for his behavior
