Responses
I'm just gonna say my theory here.
That kid is the ML and FL's child, but something happened in the future with the FL or the household crumbled leading the ML to have regret, especially with the way he treated the FL. The child realized this and somehow made it so that ML could rewind time and fix his wrong doings. The child manipulated the ML's dream so that he could talk to him. (Bullshiting)
Is that their child?
Possible the necklace grant MC's wish so that's why ML changed
Or
Possibility of ML going back in time