Escaping the hustle and bustle of Edo, the Young Lord came to Oshima Island in Izu to take a vacation. Unexpectedly, the island's boss, Amimoto, was brutally murdered with a harpoon. As usual, the Young Lord sets out to solve the case. However, most of the islanders have a grudge against Amimoto, and there are so many suspects that he is at his wits' end this time. Set against the beautiful sea of Izu and the majestic Mt. Mihara, the Young Lord's brilliant deductions and his secret sword Ichimonjo-Kakureshi cut through the mystery!