How to say "maniac" in Japanese

• マニアックCommon
  na-adjective, nounCovers the enthusiast sense of 'maniac', as in a rabid sport fan. A common loanword for someone with intense, obsessive devotion to a hobby or field, and the straightforward choice for this meaning.
  先日せんじつ、パソコンショップでＳＩＭＭの掴み取つかみどりをやっていた。いくらなんでもマニアックすぎる。↗

  I grabbed as much SIMM as possible in the computer shop the other day. Say what you like, it was more than just enthusiasm.
• 基地きちJLPT N2approx.Common
  noun (suffix)Internet slang, jocular and humorous, for an enthusiast, fanatic or nut. Suited to playful online banter rather than neutral description, so it is seldom the word you want for ordinary 'maniac'.
• キチガイCommon
  noun, noun (suffix)Covers mania, craze and obsession, and can also mean an enthusiast, but it is a sensitive word, usually written in kana alone; take care before using it for 'maniac'.

Use 「マニアック」 for a rabid enthusiast or obsessive fan; 基地 is jocular internet slang for a fanatic or nut; 「キチガイ」 covers mania, craze or obsession but is sensitive, so use it only with caution.

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

• マニアックmaniac (as in rabid sport fan)
• 狂きょうmaniac
• キチenthusiast
• 基地きちenthusiast
• きちがいmania