Mystery In is an escape room center in Busan that runs hotel-concept rooms and horror or story-driven rooms. Its themes include Usimaeul and Nokidszone, and the puzzles and devices follow one another in sequence. Hints can be requested within the time limit, and Nokidszone is not high in difficulty while Usimaeul is hard for beginners. Three themes have been played back to back during a two-day, one-night trip to Busan.