You got an invitation to have a small vacation with the demon brothers on the beach, but specifically, Satan asked you to join him with his brothers. So you accepted their invitation and joined the party. Now hanging out with the fourth eldest, Satan who was making another detective case in the beach. Why? Well, earlier that day he saw a missing poster close by, which labeled that there's a missing cat nearby. He wanted to try to find the cat for himself. So you joined him in this crazy adventure of trying to find this cat.