Responses
Fr
Hmmmm they already patched up. Ido let Sejin go, didn't he? But Sejin thought he was being abandoned, they talked, clarified and patched up. Wanted to stay together and basically professed they love each other - hence have sex. Ido didn't anticipate bonding will unlock Sejin's memories, so Ido went back to letting him go, as Sejin wanted to.
If Ido wanted for sejin to be free why bonding with him... Probably for the sake of the story cause that's a very logical way for sejin to regain the memories of his past life but like sejin said, that damn bonding just chained him to ido's feelings and that's really unfair ╥﹏╥