接続・逆接N3
〜せいで
because of... (negative) / due to...
Structure
V/い形（普通形）+ せいで；N + の + せいで
Explanation
Indicates the cause of a bad result, "because of...", with a tone of blame. Attaches to plain verb/adjective forms or の + noun. Contrasts with おかげで (positive).
Examples
寝坊したせいで、電車に乗り遅れました。
Because I overslept, I missed the train.
雨のせいで、試合が中止になりました。
The match was cancelled because of the rain.
Note
せいで is for negative results with a blaming tone; use おかげで for positive ones. せいか means "maybe because...".