A Visual Novel - Dungeon Crawler hybrid where you play as 1 of the 4 young and beautiful girls who recently died but is brought back to life by a devil (who also happens to be a young and beautiful girl).
Though, instead of claiming your ever so cliche human soul, the devil demands a huge sum of money for payment. You also learn of the dreadful fact that you will die again if the payment is not in time.
Thus begins our heroine's adventure to explore the demon world and somehow pay her debt before the deadlines.
Despite the dark sounding premise, the majority of Serment will be light-hearted slice of life events (more commonly known as cute girls doing cute things)