JoJo's Bizarre Adventure Book Club (Volume 5) 「最後の波紋」

Japanese Language Book Clubs
13

It appears to be exactly what you said. HTML Standard - the ruby element

<ruby><ruby>東<rt>とう</rt>南<rt>なん</rt></ruby><rt>たつみ</rt></ruby>の方角

東とう南なんたつみの方角

Therefore, in this example, 危き険けん、、な 、秘ひ密みつ、、を 、

As a matter of fact, [Userscript] Forum: IME2Furigana broke just now. It doesn’t account for this scenario.