1. Hiragana Fundamentals
Hiragana is the phonetic backbone of Japanese grammar; every particle, verb ending, and native word can be spelled in it, so full command of the 46 base kana plus dakuten/handakuten and combination sounds is non-negotiable before kanji.
46 basic hiragana across the a-i-u-e-o vowel rows (あいうえお ... わをん); dakuten (゛) voices か$→$が, さ$→$ざ, た$→$だ, は$→$ば; handakuten (゜) turns は$→$ぱ; small っ doubles the following consonant (きって kitte, "stamp"); small ゃゅょ create combination sounds (きゃ kya, しゅ shu, ちょ cho); long vowels are marked by doubling the vowel kana (おかあさん okaasan).
Don't confuse し (shi) with つ (tsu), or ん (n) with そ (so) / る (ru) --- these near-identical shapes are the \#1 reading-speed killer on Section II Part B.
On listening passages, students hear a doubled consonant (small っ, e.g. きって kitte "stamp") but transcribe it as the single-consonant word (きて kite "come/wear"), completely changing the meaning tested.
46 kana $arrow$ grammar glue; watch し/つ and ん/そ/る shapes.