>>5257769To East Asians, English is one of the most difficult to learn (because it lacks inflection rules like other European languages), however for native English speakers, East Asian languages are the most difficult to learn (because of the extensive grammar and phonetic rules and their exceptions).
Japanese is similar to Russian, in that it is complicated by its own grammar more than its vocabulary, but it is most complicated by the difference in the orthography and the phonetics. Most Japanese school students are required to learn only about 4,000 Kanji and all of the Katakana and Hirigana, and knowing when to formally use them and of course proper Japanese grammar. Spoken Japanese is simpler than spoken Mandarin, but Japanese written and unwritten grammar and the gradual metering and complicating of the Japanese writing system led to multiple ambiguities in spoken and written Japanese, so that even many Japanese people can become confused by these ambiguities between the orthography and the phonetics (which ironically is part of the necessity for the addition of more features to their writing system over time, which also further complicated it)