Guarding the Sacred City on the Frontier, He Accidentally Became the God of War

My name is Li Kai, and I have traveled to a fantasy world where there are four races: humans, demons, monsters, and gods. It is very scary. He is a commoner with mediocre talent. He can only join the demon-suppressing army under the human race Immortal Court and live a life of idleness. Until he received a letter from his father at home, saying that his younger brother passed away unexpectedly, and that if he did not return to fulfill his filial piety, the ancient family would have to forfeit future generations. Ever since, the human race was shocked. The commander-in-chief of the demon-suppressing army resigned and returned home. —— Ps: It's a fantasy plot, not the beginning of Return of the God of War. This novel and its characters are purely fictitious. Any similarity is purely coincidental and should not be imitated.