もの が ふるえる と、まわり の 空気 も ふるえて 波 に なります。
その 波 が 耳 に 入り、わたしたち は 音 を 聞きます。
Why six school grades, and not N5–N1?
Because that is how Japanese children learn to read. Japan's Ministry of Education fixes exactly which character belongs to which grade — so "grade 3" is a boundary you can verify, not a feeling. Every article here is machine-checked: if a single character sits above its grade, it is not published.
The result: you never hit a character you have not learned. That is the whole reason this product exists.