six / the sixth hole of a wind instrument

six

行っていらっしゃい: alternative form of いってらっしゃい (itterasshai)

see you later (said by a person staying, a stock phrase required by the Japanese etiquette, lit.: (after) going, come back)

twenty-sixth day of the month

(humble) alternative form of いってきます (itte kimasu)

back and forth

(colloquial) Synonym of 行って来ます (itte kimasu, “see you later”)

to go and come back

not straightforward; not dealt with by ordinary means