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Being strict with oneself and one's student with 心を鬼にする

Idiom Explanation: Taking a hardhearted stance with 心を鬼にする

Manga panel from 名探偵コナン showing example of Being strict with oneself and one's student with 心を鬼にする.
名探偵コナン » Volume 16 » Page 91

Conan’s classmates aren’t fond of their new teacher’s strict attitude. Ms. Kobayashi explains how at her last school, she couldn’t bring herself to be strict, and it allowed her students to get so out of control that students were injured in a fight.

小林(こばやし):
「だから、この学校(がっこう)では二度(にど)とあんな事(こと)は繰(く)り返(かえ)すまいと…」
“Therefore, to keep from repeating that kind of situation at this school...”
「心(こころ)を鬼(おに)にして自分(じぶん)にも生徒(せいと)にも厳(きび)しくしてきたの…」
“I hardened my heart and became strict, with myself and with my students...”

Key Points

  1. 心(こころ)を鬼(おに)にする = harden one’s heart

    • This idiom means to suppress softer feelings and take a stern stance.

    • In the scene, the teacher is saying she forced herself to be strict for everyone’s sake.

  2. 〜にして links the idiom to the following action

    • 心(こころ)を鬼(おに)にして means “making my heart like an ogre” and then…

    • What follows is the concrete result: she treated both herself and her students strictly.

  3. 〜てきたの looks back on an ongoing policy

    • 厳(きび)しくしてきた means she has been strict up to now.

    • The final の gives explanatory softness, fitting a sincere confession.

See Also