Ayako Kai is the boss of mission 9 in the PC Engine version of 1943 Kai.
Details[]
Ayako Kai is a revision of the original Ayako, with the multiple smaller engines replaced by two much larger ones, underwing stabilizing floats replaced with proper fuselages projecting from the rear of the propeller engine housings, and what appears to be some sort of a booster added at each of its three tails. The design of Ayako Kai is very similar to Leviathan from 1941: Counter Attack.
This boss has a few new tricks, in the form of missile weapons, in addition to the regular bullet patterns used by the original Ayako. Some of these missiles are homing weapons and leave trails of bright exhaust flames whereas others are directly fired at the aircraft's rear but have a dark body color, which often camouflages them well against the background of the boss stage and could potentially catch the players off guard.