決きめ込こむ

godan verb (-mu), transitive verb

assume; take for granted; jump to the conclusion

Used when someone firmly decides something is true without sufficient evidence, often with a negative connotation of being presumptuous or stubborn.

• 彼かれは私わたしが賛さん成せいすると決きめ込こんでいる。

  He takes it for granted that I will agree.

• まだ結けっ果かが出でていないのに、失しっ敗ぱいだと決きめ込こむのは早はやい。

  It's too early to jump to the conclusion that it's a failure when the results aren't out yet.

godan verb (-mu), transitive verb

pretend to be; pose as; feign

Often used with nouns or adjectives to indicate acting as if one were something or in a certain state, e.g., 知らん顔を決め込む (pretend not to know).

• 彼かれは知しらん顔かおを決きめ込こんで、質しつ問もんに答こたえなかった。

  He pretended not to know and didn't answer the question.

• 彼かの女じょは被ひ害がい者しゃを決きめ込こんでいるが、実じつは加か害がい者しゃだ。

  She poses as a victim, but in fact she is the perpetrator.

godan verb (-mu), transitive verb

persist in doing; go through with; make up one's mind to do

Emphasizes a strong determination to carry out a decision, often despite obstacles or criticism. Can imply stubbornness.

• 彼かれは反はん対たいされても自じ分ぶんの計けい画かくを決きめ込こんだ。

  He persisted in carrying out his plan despite opposition.

• 一いち度ど決きめ込こんだら、彼かれは絶ぜっ対たいに諦あきらめない。

  Once he makes up his mind, he never gives up.