This item is an injection-plastic aircraft model kit.
Assembly Guide
A limited-release "twofer" of the 1/72 Seiran and Nanzan kits. The Seiran was an attractively-designed float attack aircraft designed to be submarine-based. Never saw active duty, however. The Smithsonian Institution has completed restoration on the only remaining Seiran, and Tamiya contributed a nice sum to the project, hence their interest (or at least their president's interest) in this rather obscure aircraft. Kit includes optional position boarding steps and parts for a beaching dolly.
Just two Nanzan were produced as two-seat trainers for the Seiran. Without the big floats, the plane didn't need the large tail fin, and the folding upper section was removed.