In the star calendar year 2025, a space-time rift appeared on the earth ten thousand years ago. The invasion of alien beasts caused heavy casualties to humans and the population dropped by 60%. The survivors awakened their powers and controlled the alien beasts, and eventually formed a federation to block the alien beasts in the cracks. The protagonist Ye Yun is an ordinary high school student. When he was a child, cracks appeared near his home, and his parents died trying to save him and his sister. The younger sister awakens her powers and attends a school for supernatural powers, while Ye Yun awakens the Mountain and Sea System and can unlock the strange beasts from the Book of Mountains and Seas by completing tasks to fight as summoned beasts.
Ye Yun gradually grew up relying on the system, but he was jealous and hindered by the traditional forces. They were afraid that Ye Yun would break the existing order and monopolize the resources of the exotic beasts. Ye Yun is faced with a dilemma, whether to use the power of the system to become stronger quickly by any means necessary, or to stick to the bottom line and protect human justice. At the same time, the rift in time and space is unstable, and a large-scale wave of alien beasts may break out again at any time. He must increase his strength to protect the earth within a limited time.
While growing up, Ye Yun got to know the heroine, but he was torn between protecting his sister, remembering his deceased parents, and his feelings for the heroine. Moreover, he was misunderstood by traditional forces as a careerist trying to monopolize the power of exotic beasts, and faced a crisis of trust. However, Ye Yun relied on his tenacity and system assistance to continuously break through difficulties, and finally defeated various alien bosses, mastered all resources, and solved the alien beast crisis. In the end, he chose to live in seclusion in the city and opened a strange beast breeding shop.
