Warui Otoko no Gokujou Ai is a Japanese novel of 109,320 characters, with 6,653 unique words and 1,569 different kanji. Its difficulty rating on Jiten is average, 2.7 out of 5. The full vocabulary list ranks all 6,653 words by how often they appear, and you can study them on Jiten or download them as an Anki deck.
Here are some of the words that appear most often in this media, as well as a sample of its rarer vocabulary.