The Tale of the Seven Lords

The Tale of the Seven Lord (often shortened as TSL) is a series of fantasy novels written by a human named Christopher Peugeot. It has 138 volumes and according to Leviathan, it's the most widely-read fantasy series in the world.

TSL has theatrical versions, an animated series, feature films and has been translated into 182 different languages.

Story
The protagonist is called Henry, and the story seems to focus on him dealing and helping the title characters. The seven lords are brothers, the oldest being the Lord of Corruption, who's always plotting and planning in secret. The second oldest is the Lord of Fools who'd do anything for money. The third brother is the Lord of Shadow, a brooding reculse. The fourth oldest is called the Lord of Masks, who acts as a high-status, upstanding member of society, but in truth he's inhumane and cruel. The fifth brother whose name is the Lord of Lechery has a dirty mind and only thinks about seducing others. The sixth oldest is the Lord of Flies and he only has one thing on his mind - food. Lastly, the seventh brother is called the Lord of Emptiness, who's hard to understand or read.

Trivia

 * All the lords are heavily based on the seven demon brothers, while Henry is based on MC.
 * Leviathan thinks the 1990s thetrical version was an "utter disaster" due to the fact that they added characters who weren't in the original manuscript.
 * In contrast, Leviathan praises the 2015 version.
 * Leviathan says that many people like the oldest lord the best, but his favourite is the third lord.
 * He likes Henry too, to the point that he names all of his pets after him, and admits he'd like to cosplay as Henry.