Why experimental guided weapons were not fleet-ready

Did Japan possess shipboard anti-aircraft missiles near the end of the Second World War?

Possibly at an experimental level, but evidence is uncertain and neither guidance nor operational maturity appears adequate for consistent combat use.

Reports of Japanese shipboard anti-aircraft missiles remain uncertain because firm evidence has not been found. A radio-beam-riding concept derived from contemporary control technology was technically imaginable. The larger problem was turning an experimental mechanism into a weapon that could guide reliably against a moving aircraft. Fragile systems pass through an awkward initial operating stage in which minor errors defeat them, so existence on paper or aboard ship would not make the weapon combat-ready.