I'm not sure specifically as I haven't read this particular novel. But generally, a 'barbaric proposal' in a novel could potentially revolve around a very extreme or unethical suggestion made by a character, perhaps related to power, survival, or revenge.
Since I haven't read this novel, I can't say for sure who the main characters are. But usually, in a novel with a controversial concept like a 'barbaric proposal', there would be a character who makes the proposal. There might also be a protagonist who opposes it, someone who represents the moral side of the story.
The main idea could be a complex web of power, passion, and moral choices. It might center around a controversial offer that leads characters into uncharted territories.
The main features of a business proposal manga are concise yet comprehensive content, colorful illustrations to draw attention, and a logical sequence of presenting information. It aims to make complex business concepts accessible and interesting to the audience.
A business proposal manga usually has clear visualizations of the proposed plans and strategies. It might also feature characters discussing the pros and cons in an engaging way.