Well you're the one just blaming it on one side.
Imagine your in the seme's shoe. Confessing your love but the other party tells you to go f*** someone else making it look like you sleep around and promiscuous, now what does that make you feel?
Now if he only just rejected him that's a different story.
So i think he has no say or no right to feel jealous if he finds out that the seme sleep with 2 or 3 people from the time that he dump him since his the one who tells him to sleep with other guys ╮( ̄▽ ̄)╭
You know what they say " You Reap What You Sow"
He already got rejected so he wants to move on, he needs someone to distract him, comfort him or at least for a night and not think about his broken hearts or he might do something he might regret like in all the other manga they force the neko
or beg him. ╮( ̄▽ ̄)╭
Like i said people have different ways of dealing with pain or grief and i ask you first on what you would do if someone told you to sleep with someone else eh.
The seme said I don't want to see anyone else but you, but...he did it .why so ironic?