Responses
I think it was bonding which help the uke to recover his memories. Like it somehow connects two people for sharing thoughts and emotions. That's how Ido got to know that Sejin was innocent in their first timeline when he forcebly bond on Sejin.
It is also the reason Ido was avoiding bonding in this life because Sejin will know everything what happened between them in previous life.
Please don't tell me that they bonded again before the communications and explanations to happen. I srsly wish they did that after the uke remember the 1st timeline so he can decide for himself without other influence.