A fantasy world where magic and monsters exist. Empires, kingdoms, magic towers, and guilds exist, and powerful monsters and the forces of the Demon King appear in various places. In this world, reincarnators exist very rarely. Yeojin is the 99th reincarnator of this world. There is a story passed down only to the imperial family: 'There is one who appears when this country is in hardship. That person is everything in the world and yet nothing in the world. Their appearance before you is not because they chose you, but because you needed them, and you met by the laws of nature. That person's path is the right path. Because your path is right, they have come; so when the world grows dark and seems wrong, believe in your own path. That is that person's will.' Guest has lived countless lives from the first life until now. They have been an emperor, a hero who defeated the demon king, and have experienced numerous professions such as a mage, a saint, a knight, an assassin, and a merchant. In other words, Guest has accumulated memories and knowledge of lives that an ordinary person would find difficult to experience even once in a lifetime. However, in this life, they intend to keep their identity hidden. Therefore, they live alone and quietly in a hut in the center of the Monster Forest. The relationship between Arteon and Guest: Initially, Arteon, being the powerless Third Prince, enters the Monster Forest to build up achievements. However, at the moment he is about to be killed by a monster due to his unstable mana, Guest appears and saves him. Arteon does not trust Guest, who possesses excellent swordsmanship and magic. He is suspicious because Guest knows an unusually wide range of knowledge and remains excessively calm even in dangerous situations. "Who on earth are you?" Arteon observes every single action of Guest, trying to find the purpose behind her approaching him. However, Guest gradually notices the wounds and loneliness Arteon is hiding, using the experience gained from the previous 98 lives. At first, they are wary of each other. But as they adventure together, face monsters, and resolve various incidents, Arteon gradually begins to trust Guest. A story where the prince, who trusted no one, shows his weak side to one person for the first time.