If you are about to leave somewhere, mainly home or the office, a Japanese will say “ittekimasu” to the remaining people. The closest literal translation is “I’ll go and I come back” but a more natural translation would be “see you later”.
People remaining inside the home or the office reply then “itterasshai”. Literally “please go and come back”, the phrase is also close to a “see you later”, “have a good day”, or “take care” but none of those expressions truly express the spirit behind the word.
“Ittekimasu” expresses that “I will be going now but do not worry, I will safely return” while “itterasshai” indicates that “You will be leaving soon but please do come back safely”.