against; contrary to
Used to indicate that something goes against expectations, rules, or a previous statement. Often follows nouns or nominalized phrases.
See also: 反する
予想に反して、試験は簡単だった。
Contrary to expectations, the exam was easy.
法律に反して、その建物は建てられた。
The building was constructed against the law.
Derived from the verb 反する (はんする, 'to be contrary to') combined with the particle に and the te-form して, forming a set phrase meaning 'contrary to'.