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

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:
- 「だから、この学校
( では二度( とあんな事( は繰( り返( すまいと…」- “Therefore, to keep from repeating that kind of situation at this school...”
- 「心
( を鬼( にして自分( にも生徒( にも厳( しくしてきたの…」- “I hardened my heart and became strict, with myself and with my students...”
- Literal: “I made my heart a demon and became strict with myself and with my students...”
- “Therefore, to keep from repeating that kind of situation at this school...”
Key Points
- 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.
- 心
( を鬼( 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.
- 厳
( しくしてきた means she has been strict up to now. - The final の gives explanatory softness, fitting a sincere confession.
Vocabulary
自分 (Oneself)
自分
( means oneself, myself, or yourself depending on context. It originally points to one’s own share or allotted part, and from there to the self.学校 (School)
学校
( refers to a facility or place where teachers provide education to children and students in an organized manner, following specific plans and objectives.二度 (Twice)
二度
( refers to the same action or situation occurring twice. It can refer to frequency (something happening twice) or order (being the second in a series).
See Also
- External: Past tense with 〜た・〜だ
- Grammar: Marking the topic with は and も
- Kanji: Dividing and portions with 分
- Kanji: Measures and degrees with 度
- Kanji: Schools and checking with 校