
I doubt it at first but now im sure....the theme is similar to The Palace Of Bardo (tho that one is much heavy)
Basically, there's two timeline. We have the knight (MC) and the emperor.
The first one is when MC become a hostage after the war and was sold to the yellow hair emperor, where the emperor did nasty things to him and keep him as a possession.
The second timeline is MC second life (he reincarnated and remember what happened in prev life). In this life he ran away from the place (which might lead him to the emperor), choose different path but eventually met (probably) the reincarnation of the emperor (grey hair).

I like the fact that keira is ready to face Colette.
Also, my guess is (probably everyone can perfectly guess this too) the other person who casted the time turn magic is the father, and he let her daughter to get the memories so she can redeem and save her life.
About why the magician help her....maybe he is indebted to the grand duke OR he likes her (but its hard to guess can if he does, she must've remember it, but she didn't have any memory of meeting him before)
Hence idk who is the ML, her knight or the magician (both are good)

spoiler
romance is basically non-existent in this story; making mls non-existent too (if we're basing it on the novel) and yes, it was keira's father who casted the time turn magic along with the magician. and i guess the reason why the magician did the magic was because of the previous timeline (where keira died) the world became chaotic and that's when the duke knew he fucked up so leaving the magician with no choice, they gotta rewind the time in order to atleast, change the future.
Me at first : oh yeah new spy action story
Me after the fight : sorcerer? magic??????
( ̄∇ ̄")
ps : pretty sure the boyfriend is someone higher in the line of field as well. He clearly knew what the MC job are.