How To Spot A Japanese Porn Novel

They use bigger fonts.

Seriously. If you compare a naughty novel (of the sort I’ve been collecting covers from…) to a regular novel with the same page size, the one with larger kanji is the one full of hardcore sex scenes. Light novels, mysteries, literature, food guides, science fiction, etc: small font, variable amount of furigana. Porn: 20% larger font, very little furigana.