Here's the answer:
“いってきます”
(ittekimasu)
Watch a real native speaker say it:
Here's how it sounds in a textbook:
Fun fact: the hundreds of thousands of people learning Japanese with Memrise get this phrase correct 87.96% of the time!
(ittekimasu)
Fun fact: the hundreds of thousands of people learning Japanese with Memrise get this phrase correct 87.96% of the time!