Travel to the World of Fate and Become a Servant

Luo Xiaohan was posting in the Fate community when a pop-up box suddenly appeared in front of him. The system and the boss of a certain red-clad Archer decided to let him participate in the Holy Grail War. The system could not tolerate his refusal, so the system teleported him directly to a girl. Under his feet was the red circle summoning the servants, and he became the girl's Caster. Other servants can fight and run, but our servant cannot fight, and is regarded as the master. When encountering problems, he will post for help. However, he can summon servants through the system! So, who is the powerful Servant? Just when he was curious, a red figure appeared in the bullet box.