せいだ

it's someone's fault

→ せい
phrase Very common #1,645
it's someone's fault Used to blame someone or something for a negative result. The person or thing being blamed is marked with の, as in お前のせいだぞ (It's your fault!).
JA: お前のせいだぞ。
EN: It's your fault!

集会召集したのはマクサンス酷いことをしたせいだ

The meeting was called because something terrible had been done to Maxence.

— コーラス (2004)

彼は自分の成功は努力したせいだと言った

He said that his success was due to his hard work.

彼が家を飛び出したのは父親が厳しかったせいだ

He ran away from home because his father was strict.

下痢そのせいだ

That’s also what caused the diarrhea.

— 火垂るの墓 (1988)

多分今日トム来てないのはそのせいだ

That's probably why Tom isn't here today.

環境が変わったせいだ

It's because the environment changed.

— 箪笥<たんす> (2003)

私のせいだ

It's my fault.

— オッペンハイマー (2023)

お前のせいだ

It's all your fault!

— ANORA アノーラ (2024)

マネージャー失敗は自分のせいだといった

The manager said the failure was their fault.