by inches

Very gradually; by small degrees.

Japanese Meaning

非常にゆっくりと、僅かな単位で徐々に変化するさま。 / ごくわずかに、段階的に物事が進む様子。

She improved her painting skills by inches, practicing a little every day until her brushstrokes were confident.

彼女は毎日少しずつ練習して、筆遣いに自信がつくまで絵の技術を向上させた。

Sense（1）

Very gradually; by small degrees.

to kill by inches