I recommend "Demon Survival Game" to you. This book tells the story of a group of people who are trapped on a mysterious island. Each of them has a different identity as a "demon." The protagonists needed to constantly become stronger and evolve in order to survive. In the process of exploring the island, they revealed the secrets of the real behind-the-scenes big shots and demons. There is also a butler character in this novel who pays special attention to survival skills and mastering survival skills. Perhaps it is similar to the butler on the island you mentioned. I hope you like my recommendation. Muah ~