SPOILER (even if everyone basically knows it)
The baby was made during the first time they had sex, in chapter 10, when Hyesong was in heat and kinda forced himself on Dojin (from what I understood). I'm not sayin' Dojin didn't forced himself on Hyesong after that but the baby wasn't made during rape ! I think it's kinda important so stop sayin' "Oh Dojin wants to use pregnancy to keep Hyesong"
I saw many comments saying that this is season 2 but it's actually season 3. Season 2 was from chapter 20 to chapter 35 (on lezhin's website).
I just wanna say that this manhwa is pure masterpiece. It describes so well these two guys's psychological problems. I love all this so much that I even love the both of them ^^