He believes Yuder's words when he doesn't even have enough evidence to prove his point other than Kishiar's faith and Kishiar trusts him with all his being, he's the one who teaches Yuder everything he learned in his past life and even though Yuder seems like doesn't like him he has admired Kishiar for 11 years and the only one he respects enough to take commands is Kishiar like you won't ever regret reading the novel. 

You can read it in novelingua