You should treasure every encounter, for it will never recur.

excuse me; may I come in?

parting, parting ways

the first in grade or rank

one case, one matter

Kyūjitai form of 一体: on earth, the heck, in the world (used for emphasis and to express incredulity)

a complete set of something, a complete suit of clothes

one example

once / temporarily, for the time being / tentatively, just in case

the first or foremost place, first rank / (mathematics) a digit in the ones, 'unidigit' / (historical) the first-in-rank in the Japanese medieval court