Japanese is the world's most complicated writing system because it utilizes four different systems: two syllabaries, Kanji (Chinese-derived characters), and the Roman alphabet.

The finding

What the evidence shows

It is true that written Japanese combines two syllabaries, kanji borrowed from Chinese, and the Roman alphabet, and this combination is often called one of the world's most complex writing systems in casual and popular sources. But calling it definitively the single most complicated system in the world overstates the case, since linguists don't have an agreed way to rank writing systems by difficulty and other complex scripts have their own strong claims. The facts about the four systems are accurate, the superlative ranking is opinion dressed up as settled fact.

No supporting source was captured. This finding should not be treated as a sourced conclusion.