What it means
くせに means “even though” or “despite,” with a strong sense of criticism, blame, or surprise at a contradiction. It presents a fact that should normally lead to a different result, often suggesting that the subject has no right to behave in the stated way. It follows the plain form of verbs and i-adjectives, and the noun or na-adjective form plus な. The main clause can be either familiar or polite.
Usage note
くせに is more judgmental and confrontational than のに, so it is not suitable for neutral statements. The subject of the clause before くせに is usually the same as, or closely related to, the subject of the main clause. In polite sentences, くせに itself does not change; politeness is expressed in the main clause.
How to use it
彼は学生のくせに、宿題を提出しません。
Although he is a student, he does not submit his homework.
彼女は元気なくせに、薬を飲んでいます。
Although she is healthy, she is taking medicine.
この店は安いくせに、料理が少ないです。
Although this restaurant is inexpensive, the portions are small.
兄は毎日運動するくせに、体力がありません。
Although my older brother exercises every day, he has no stamina.
彼は学生のくせに、宿題を提出しない。
Although he is a student, he does not submit his homework.
彼女は元気なくせに、薬を飲んでいる。
Although she is healthy, she is taking medicine.
この店は安いくせに、料理が少ない。
Although this restaurant is inexpensive, the portions are small.
兄は毎日運動するくせに、体力がない。
Although my older brother exercises every day, he has no stamina.
Example sentences
新人のくせに、部長の指示を無視して勝手に計画を変更した。
Even though he is a newcomer, he ignored the department manager's instructions and changed the plan without permission.
何も準備していないくせに、彼は試験の結果に文句を言っている。
Even though he did not prepare anything, he is complaining about the exam results.