These are examples of more creative use of the classes added by the Furikanji add-on.

Markers for furikanji

I use markers that show the beginning and end of a specific block of readings:

Text: 起きなよいい加減お
with きなよいいかげん as ruby and きなよいいかげん with 起きなよいい加
減お as ruby. The kanji of the ruby are marked with vertical bars.
Example use of furigana and furikanji. The source of the text is an Anki-2-ified version of the sub2srs example deck 「時 を掛ける少女」.

To use furikanji, with the markers shown, i use

.redish { color: #a00;}
.furikanji:before, .furikanji:after {
    font-size: 50%;
    position: relative;
    bottom: 2rem;
    width: 0px;
    vertical-align: baseline;
}
.furikanji:before { content : "|"}
.furikanji:after { content : "|"}

as styling and

<div>{{Image}}</div>
{{Audio}}
<div class="nhg lnsz">{{furigana:Reading}}</div>
<div class="nhg redish lnsz">{{furikanji:Reading}}</div>

as back template.

Separator for kana

Some people like to use the interpunct to separate the kana for different kanji. For example, for the word 中黒 the text なか・ぐろ is used in a reading field.

An alternative is to use the Japanese Support add-on to automatically generate readings. They are usually by word, and have to be rearranged slightly by hand. In the example, you would type the kanji中黒 into the Expression field. With a tab or mouse click, the Reading field would be filled with 中黒[なかぐろ]. For this trick to work, this string would have to changed to 中[なか]黒[ぐろ] by hand, by adding an extra pair of square brackets and dragging theなか into them.

The adding of the interpunct can be done using two CSS pseudo-classes, :after and :last-child:

<div class="interpuncts">{kana:Reading}}</div>
.interpuncts .kana:after{content:"・";}
.interpuncts .kana:last-child:after{content: none;}

The advantage of this method over using pure kana is that with this method furigana can be used as well, with {{furigana:Reading}}.

Furigana on hover

This method works without this add-on as well.

To show furigana only when the mouse hovers above it use:

<div class="kanjihover">{{furigana:Reading}}</div>
.kanjihover rt{visibility: hidden;}
.kanjihover ruby:hover rt {visibility: visible;}

or to activate this for all furigana everywhere, drop the extra class:

{{furigana:Reading}}
rt{visibility: hidden;}
ruby:hover rt {visibility: visible;}