The N1K2-J, designated as Shiden Kai Mod. 21 (紫電改二一型), was developed very shortly after the N1K1-J Shiden was accepted into service, addressing most of the flaws of the previous model. The wings were moved to a low position, which permitted the use of a shorter, conventional undercarriage. The fuselage was lengthened and the tail was redesigned. The production of the entire aircraft was simplified; it was lighter by 250 kg, faster, and more reliable than its predecessor. Although engine issues were still a problem, the Homare couldn't be replaced as there was simply no alternative.

In the game since the start of the Open Beta Test prior to Update 1.27, the Shiden-Kai is a challenging aircraft to master. It has superior manoeuvrability over early jets, but they have a significant speed advantage. The only jet that can rival its agility is the Yak-15, but it suffers from low speed, climb rate, and ammunition. The N1K2-J can easily outperform most conventional propeller planes, but it faces difficulties against other superprops, which have better overall performance. The N1K2-J should rely on its mid-speed handling to gain the upper hand in dogfights. In ground battles, it can excel as a fighter-bomber employing two 250 kg bombs or Type 5 rockets next to its four 20 mm cannons which can load a solid belt of AP which can reliably destroy soft targets and top-down medium armoured vehicles.