Why would a light novel have furigana for common kanji?

Question

I've been reading the light novels ひげを剃る and a lot of the furigana use confuses me. For context, not every kanji has furigana- I'd say like 20% of the kanji per page have it.

They use it for complicated words that seem like they should have it, like 茫然自失｛ぼうぜんじしつ｝、but then also with random common words like 笑顔｛えがお｝、一緒｛いっしょ｝に、吐｛は｝く、大丈夫｛だいじょうぶ｝、違｛ちが｝う etc.

Given the themes of the story I'd assume it's targeted to young adults, so why does it give the readings for really common words in addition to ones that look complicated, at least to me?

Answer 1

In general, furigana rules tends to be determined on a per-magazine or per-bunko-label basis, and the theme of each title is not always relevant. Titles published in 少年向け ("for early-teens") labels/magazines, such as 週刊ジャンプ, have lots of furigana even though individual titles sometimes contain adult-oriented themes. Titles belonging to ヤング/青年向け (for high-teens and young adults, such as ヤングジャンプ) or 大人/成年向け (for adults) labels/magazines tend to have much less furigana even though some titles are safe for children.

角川スニーカー文庫, as a sub-label of 角川文庫, has historically targeted at 少年 generations, so I expect more furigana than average. I checked some titles listed here, and found that many titles of this label are like ひげを剃る, too, although there seemed to be exceptions.

Answer 2

It seems they add furigana to kanji that are not taught in elementary school (小学校).

緒、吐、丈、違 are not taught in elementary school. (参考: 学年別漢字配当表)

[笑]{わら}う is taught in 4年生, but the readings [笑]{え}む、[笑]{しょう}、[笑顔]{えがお} are taught in junior high school (中学校). (See pages 24 and 51 in 音訓の小・中・高等学校段階別割り振り表 平成２９年３月)