Not a spoiler, this is just my personal opinion... That's what I thought after reading what Ja-kyung said at the end... And about his stepmother, from the moment she appeared, she wanted Hyeon to die by any means so that her child would inherit all of her family's assets...
That's all just personal opinion from the latest chapter... I won't give spoilers without warning. ┑( ̄Д  ̄)┍

In the end, it was his own father who wanted to kill his son... What a deeply troubled family... His stepmother is just as crazy...( ̄∇ ̄")
The more Ja-kyung wants to kill Hyeon, the more impossible I'm sure it will be haha... Because it seems like Ja-kyung is getting deeper into a situation she shouldn't know too much about. ╮( ̄▽ ̄)╭