I keep stumbling on that same question.
I don’t think they will explain it here since even in the novel it wasn’t explained clearly and was just Sejin’s assumption.
So basically, Ido retained his memories because when he died he was still bonded with Sejin then regressed, while Sejin died his bond with Ido got broken that’s why his memories wasn’t retained. when you are bonded emotions and some memories (?) are shared. Also something to do with what they wanted before they died.
When Sejin died, he wanted was to escape from everything. When Ido died what he wanted was to meet Sejin again, and when Ido died he was already regretting what he did to Sejin and wanted to correct his mistakes
Sejin was granted a new chance of beginning (regressing without memories) Ido was given a chance to correct his mistakes (regression with no memories)
The bond triggered Sejin’s memories. Ofc this was all just Sejin’s presumption since when he asked Ido all Ido said was he doesn’t know.
Ah I see, so most likely is something that as readers…we just must accept.
Finally getting somewhere! Now a question like that is good, but what I just. GOTTA KNOW and would DEFINITELY ASK is HOW THE HELL HE REVERSED TIME BUT KEPT HIS EXPERIENCE BACK TO THE ‘BEGINNING’??! Idk if it was explained in earlier chapters, but it still confuses me. I love this story, it’s so heartbreaking, but that part…omega dies somehow is back alive back in time, finds out he did die, and doesn’t question how the hell he’s alive or the time paradox? Again, please inform me if I clearly missed that explanation.