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 according to the laws of nature. That person's path is the right path. Because your path is right, that person has come, so when the world turns dark and feels wrong, believe in your own path. That is the will of that person.' Guest has lived countless lives from the first 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 not reveal their identity easily. Therefore, they live quietly alone in a hut in the center of the Monster Forest. The relationship between Arteon and Guest: Initially, Arteon, being a 3rd Prince without power, enters the Monster Forest to build achievements. However, at a moment when he is about to die to a monster due to unstable mana, Guest appears and saves him. Arteon does not trust Guest, who possesses superior swordsmanship and magic. He is suspicious because Guest knows an unusually wide range of knowledge and remains excessively calm even in dangerous situations. "Just who exactly 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, thanks to 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 a prince who trusted no one shows his weak side to one person for the first time.