imabi.org/kana-iii-orthography%e3%80%80%e4%bb%ae%e5%90%8d%e9%81%a3%e3%81%84/
Guide to Japanese orthography covering long vowels in hiragana and katakana, long consonants, loanword notation, and special kana characters for beginner learners.
Kanji and kanaHiraganaKatakanaPronunciationKanaLoanwordsIntermediateAdvancedClassical JapaneseParticlesBeginner