To keep something secret.
何かを秘密にする。 (Nanika o himitsu ni suru.)
"I’ll tell you a secret, but keep it under your hat."
"秘密を教えるけど、内緒にしておいて。" (Himitsu o oshieru kedo, **naisho ni shite oite**.)
To follow rules or policies strictly, often without question...
to assert your authority or make a firm decision
to open your books and begin studying
to leave something undecided or uncertain
to follow your intuition or instincts
to give someone a chance or show them mercy
