The palm-sized, lavishly illustrated paperbacks known in Japan as "light novels" can have some heavy titles. "That Time I Got Reincarnated as a Slime" is one. Another, "Is it Wrong to Try to Pick up Girls in a Dungeon?" is a bestseller, but so is "I Want to Eat Your Pancreas." And that's a love story. Of course.

They can also have some heavy political repercussions. Earlier this month, a light novel called "(New Life +) Young Again in Another World" had its big-budget anime adaptation and future publications in all languages abruptly canceled after its author, pen name Mine, was found to have posted racist tweets denigrating Chinese and Koreans. The offensive posts, first issued four years ago, were deleted, and Mine publicly apologized. But the tweets and the novel's storyline, in which a Japanese swordsman who murdered 3,000 in China is reborn in a land of monsters, were not taken lightly.

Quite what qualifies as a light novel is a subject of debate and ongoing revision. According to translator and journalist Kim Morrissy's 2016 Anime News Network article, Keita Kamikita, manager of an online fantasy and science fiction forum, coined the term in 1990 when he noticed that new types of fantasy prose narratives were drawing the attention of manga and anime fans. This burgeoning readership was not entirely young, so the "young adult" label didn't apply. Nor were they reading works that adhered to pre-existing genres such as romance, mystery, horror and so on.