Why doesn't Chen Guo, the net cafe owner, find out that Ye Xiu is the Battle God of Glory? Doesn't his friend Tan Rou who is playing with him also know it?
As I recall, Chen Guo did not believe Ye Xiu when he told her that he really is Ye Xiu, The Battle God of Glory, and Tang Rou has no idea who Ye Xiu really is.
!!! This is a spoiler from the Light Novel !!!
No worries though, because they will soon find out during the All-Star Weekend and from there Ye Xiu will tell his story.
The net cafe owner, Chen Guo, does not find out that Ye Xiu is the god of glory because she just thinks that he is another slacker addicted to the game of glory. [Taken from The King's Avatar wikia]
He asks Chen Guo about the job flyer, requesting a night Network Manager, for the cafe. Since the job hours are so undesirable, she gives him the job, which includes food and shelter. The room he is given is a storage room filled with boxes, and only a meager bed in the corner.
When the countdown for the tenth server ends and the server opens, Ye Xiu opens up a guide. He tells Chen Guo that he is actually Ye Qiu, and Chen Guo jokingly retorts that she is Su Mucheng.
No, her friend, Tang Rou, is an absolute newbie to the game and finds about the games through her friend Chen Guo. And although she understands the absolute superiority of Ye Xiu, she doesn't know that he is the god of glory until later when he starts attracting the attention of guilds and in turn pro players.