1A genre (or a work) that deals with mysteries and unexplained events, such as detective novels, movies, or dramas; can also refer to something mysterious.
休日はミステリー小説を読むのが好きだ。
I like to read mystery novels on my days off.
昨夜はミステリー映画を見て、結末に驚いた。
I watched a mystery movie last night and was surprised by the ending.
彼女の失踪は町のミステリーになっている。
Her disappearance has become the town's mystery.