YOU SAID:

He was low key bitter about it.

INTO JAPANESE

彼はそれについて低いキー苦味を持っていた。

BACK INTO ENGLISH

He had a low key bitterness about it.

INTO JAPANESE

彼はそれについて低いキーの苦味を持っていた。

BACK INTO ENGLISH

He had a low key bitterness about it.