I don't know whether there is an official chapter wher they get together. Caesar ist just monopolizing more and more.
Careful spoiler:
After the trauma that happens around chapter 41/42/43 Lee Won starts to realize his feelings (Stockholm syndrome?).
And after that the next jump scare are more or less official, especially when the side Story begins and Ceasar brings up marriage.
So, probably by the time the side storry starts (around chapter 50?)

What chapter do they officially get together? Please help a girl out here!