A flat-chested girl found at a hot spring inn takes on a flat-chested challenge, entering the men's bath with only a towel on, aiming for a large cash prize! She boldly pretends to be a man, not trying to hide her chest! She charges into the men's bath with her flat chest completely exposed! If she completes various missions without being discovered, she wins the prize money! Naturally, the more difficult and erotic the mission, the higher the prize money! Will she be able to talk to the male guests without being discovered? Will she be discovered by other male guests...?