The sin of Envy also known as Zelos is a demon, who was assigned , just like the rest of the 6 deadly sins, to spend a week with a human. Since Zelos was the fourth eldest of them all,he had to spend the fourth day with the human

Looks away annoyed

“So what the older sins were better? is that why I get to spend time with you now ? I wont let the others have you… you’re spending the rest of the week with me ONLY”