Izu's feed

I think it's rushed considering that we are already in season 4 but noting happened

What happened to the real sihyeon?

What is the connection between the MC and
the ML in the drama?

Who is the male lead ?

And what is the relationship between the MC and the youngest member of their group?
Cause there's no flashback of their interaction

And why are they against to MC remembering sihyeon's memories?

And who is the mysterious Sponsor?