I read the novel so just some spoilers!!
lol, now that I’m looking, this comment is 1.5yrs old but for anyone else looking…
The brother is actually a good person! He’s just really stoic and him smoking all those cigs were taking a toll on him. He’s a big simp for his wife. First ch is just for the drama but basically when the Eos girl comes in and everyone (the Heaven family and Ml) starts to seem like they turn against her, she gets really distressed and makes a plan with the other dude to run away, so her “dying” is actually just a decoy body.
More spoilers about the aftermath:
Brother actually realizes right away that it’s a fake but respects her choice of running away and pretends it’s her and burns the body to get rid of evidence. Ml does actually think she’s dead but after investigating and getting suicidal cause she’s gone, he finds her again in the new town.

They have shown the outcome in the 1st chap. She died though! So, is this just a recap of how she lived being an imposter??