In section 1.5, the Japanese and English text seems contradictory as to what letter is used prior to b/m/p, in terms given in Hepburn romaji.

The English text says: "(except that "m", not "n", is used before "b", "m" and "p")" meaning that "m" will be used.
The Japanese text says: "（ただし，b，m，pの前では“m”としないで，“n”とした）" meaning that "n" will be used.

In practice, "n" seems to be used, with terms such as "kihon-hanmen", "honbun", "kanbun", etc, so the English text appears to be in error.