How to say "secretly" in Japanese

• こっそりJLPT N2approx.Common
  adverb (with と)Covers doing something secretly so as not to be noticed, with little judgment attached. Typical of sneaking a snack, leaving quietly, or hiding something without anyone finding out.
  彼かれはそのことを私にこっそり話はなしてくれた。↗

  He told me about it in private.
• こそこそCommon
  adverb (with と), suru verbAlso furtive, but the repeated sound suggests sneaky, underhanded behavior and often carries a disapproving nuance, as of someone whispering or skulking around on the sly.
  影かげでこそこそせず面めんと向むかって彼かれにそれを言いいたまえ。↗

  Say it to his face, not behind his back.
• 人知れずひとしれずCommon
  expression, adverbMeans secretly, unseen and unobserved by others, and tends toward literary or emotive use — quietly suffering, grieving, or striving where no one knows.
• そっとJLPT N3approx.Common
  adverbPrimarily stealthily or quietly, doing something gently so as not to disturb or be noticed, as in entering a room or watching someone without being seen; the secrecy is about avoiding attention.

For quiet, furtive doing use 「そっと」 or 「こっそり」; 「こそこそ」 adds a sneaky, disapproving tone; 「人知れず」 stresses that no one knows or sees, often with emotional overtones.

Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only

• こっそりstealthily
• こそこそsneakily
• 人知れずひとしれずsecretly
• 密々みつみつsecretly
• 暗々裏あんあんりsecretly
• 暗々のうちにあんあんのうちにsecretly
• 心密かにこころひそかにinwardly
• 陰にいんにinvisibly
• こそっとstealthily
• 陰ながらかげながらfrom behind the scenes (cheer, pray, etc. for someone)
• そっとstealthily