Why Japan's 25 mm AA gun underperformed

What was wrong with the Japanese 25 mm anti-aircraft gun, and why was it not fixed?

It lacked reach and stopping power, and replacing it with a 40 mm system required industrial conversion Japan did not complete in time.

The 25 mm tried to fill a medium anti-aircraft role without the characteristics that made either the Bofors or Pom-Pom effective. Japan's excellent 100 mm dual-purpose gun was difficult to manufacture and retrofit in enough numbers, leaving an awkward gap in layered defense. The Type 96 lacked the Bofors's range and stopping power while also missing the Pom-Pom's close-range volume of fire. Its weakness was therefore not simply caliber but a poor fit between intended role, mounting, and performance.