Well... That's his fault, because he sleeped beside Pepe. Naked.
It's obvious, that this blackhaired one is his soon to be ex-misstress. And all of you, who said : cheater. You can't expect him to be living like a monk, right? He's an emperor. Of course he has a possible harem. And there are just some days after he fell for Pepe.
Of course I can understand the reaction, to instantly hate her, even if she just appeared in his room. But try too understand her too, if she really is his mistress. How would you feel, if you give all for the men which you love and then a women appeared, they fall in love which each other and you would be cast aside? I know that, would my bf pull such a stand, I would turn into a monster.
Long talk short, just let's wait for the coming chapters and look, what's going to happen