beta
Ido didn’t lead him on. From the start, he planned to help Sejin separate from his toxic family and become financially independent (by having his own company) so he could stand on his own, then he will set him free. This was Ido’s atonement for his past sins. But he couldn’t help but treat Sejin lovingly and sleep with him because Ido was still in love with him. Now that Sejin is set, Ido has decided to continue with his plan.
However, based on the spoilers, he won’t be able to follow through with his plan because, in his own words, he is "greedy" and can't help but love Sejin and mark him which resulted into Sejin remembering the past (when Ido treated him badly due to misunderstandings), and the angsty plot will begin.