Shun was just an ordinary student living a lonely life. However, a mysterious explosion in his classroom brought his life as a human to an end. When he awoke, he discovered that he had been reincarnated into a fantasy world as a tiny spider. Trapped on the deepest floor of a labyrinth filled with dangerous monsters, Shun had to struggle alone to survive. By eating monsters, he gained experience, leveled up, acquired new abilities, and unlocked various evolution paths. With each evolution, his body grew stronger until he eventually gained the ability to take on a human form. However, there was one thing he never realized. From the very beginning, his growth had been watched by a woman known as the Demon Lord.