After his life on Earth comes to an end, Lynos is reborn equipped with a rare and powerful guardian magic that only a few select individuals, known as Barrier Masters, possess. Unfortunately, his fortunes take a turn for the worse as he is reincarnated as a vulnerable child who is slated to be sold into slavery. However, Lynos manages to narrowly evade his ill fate and is taken in as a servant by a wealthy noble clan. With their guidance, Lynos is trained to become the protector of the family's most important members. As he overcomes obstacle after obstacle, Lynos prepares himself for a future full of adventure and exploration as a skilled Barrier Master!