expression
only when; particularly in the case of; of all times/people
Attaches to a noun and marks it as the exclusive case where something (usually negative or unexpected) happens. Often implies 'why now/this person of all times/people?' or 'it had to be this one.'
急いでいる時に限って、バスが遅れる。
The bus is late only when I'm in a hurry.
彼に限って、そんな失礼なことを言うはずがない。
He, of all people, would never say something so rude.