せい is a word in Japanese which can be used to express blame or fault. I’ll go over a few related uses of this word.
1) Explaining something occurred because of someone or something’s fault. This is similar to using （だ）から in the sense of ‘because’ except it usually has a negative connotation.
Pattern: [reason for something] + せいで + [What happened as a result of that reason]
- Because I’m tired I can’t organize my thoughts.
- Because my hands are small I can’t play the piano well.
The way it is used grammatically changes slightly depending on the word used. Here are the general patterns:
- With a verb in the normal (する), past-tense (した), or continual (してる/してた) forms: Verb + せいで
- With a na-adjective: Adj + な + せいで
- With a i-adjective: Adj + せいで
- With a noun: Noun + の + せいで
If you want to express uncertainty in the reason, you can replace せいで with せいか
- My computer won’t start up, possibly because I dropped it.
2) Explaining a reason for something directly without talking about what happened as a result.
Pattern: [reason for something] + せい (+ だ／です)
- It’s because I’m bad at Japanese.
3) Directly blaming someone for being the cause of a negative consequence.
Pattern: [reason for something] + せい + にする
- I blame you.
- Take responsibility yourself, don’t blame other people.
If you wan’t to express something caused a positive result, you can use おかげ（お陰）in a similar way. This has the nuance of “thanks to ~”.
- I passed the test thanks to (my) teacher.
The expression おかげさまで derives from this same おかげ and is used to give thanks to those around you, or in a spiritual sense. It is often used when talking about one’s health.
- Thankfully my cold has gotten better.
Finally, both せいで and おかげで can be used after その to refer to something that was just discussed.
- That day the roads were wet and because of that, I slipped.