Mattsu and Yamma return for another round of treasure hunting, this time setting their sights beyond the familiar streets of Matsuyama. The trio, now including Moburi, ventures west toward a chain of mysterious islands rumored to hold naval riches and ancient secrets. What begins as another exciting expedition quickly becomes something far more complex when they stumble upon a series of riddles woven into the very landscape of these islands. Each puzzle solved brings them closer to treasure, but also closer to uncovering a larger mystery that threatens the region's balance. The boys' enthusiasm clashes with Moburi's more cautious approach as they navigate through obstacle after obstacle, each testing their loyalty to one another. This continuation leans into the same adventurous spirit as before, but shifts focus to the dangers lurking beyond their home city. The stakes feel higher, the challenges more elaborate, and the questions about what they should pursue grow more urgent as they realize the treasure hunt carries unexpected consequences.