While the Sumerian writing system presents some of the same difficulties of the Japanese writing system, like many signs that have multiple possible readings and a combination of semantic signs and phonetic signs, the total number of signs and the number of possible readings for them are far greater in Japanese, so the Sumerian writing system is easier and more regular than the Japanese writing system.

The main difficulties of the Sumerian writing system are due to the fact that many of its rules had to be guessed, e.g. about where to use certain readings for some signs, depending on their context, because the last people who knew the complete system have died millennia ago, and such guesses are seldom completely certain.

In the comparison with Sumerian, Japanese is aided by the existence of native speakers who can always show the correct reading and meaning of a text (though many young Japanese can have great difficulties in reading any book published before WWII, because the writing reform has made drastic changes, replacing both many kanji signs and the furigana used for many kanji signs, so even where furigana are written they may not help enough a modern reader).

However, while the availability of native speakers eliminates the problems caused by not knowing the correct rules, that still does not make the Japanese writing system simpler than the Sumerian writing system.