Is beyond me how can anyone rate this 10 stars. Is people so desperate?
To start with the first episode, the girl is suppose to suffer from major PTSD. That's NOT how PTSD effects manifest. Don't come to the usual trope "its a drama", that's not an excuse for a terrible plot.
They treat the FL as some sort of "temporarily brain damaged" person with some selective memory loss, that also sleep walks. Well you can suffer some memory loss after a big stress event, but you won't get retarded.
Second point and the most disturbing one: this is a bullying drama that wants to pass for "cute, fluffy, love". The ML is constantly bullying his sister, stalking her, not allowing her to make her own choices and friends, physically abusing her, asking her constantly to cook for him as she is his personal maid. But hey, he loves her so it's ok?...
Also her adoptive parents are constantly leaving home letting their kids alone and asking the adoptive daughter to cook for the boy, again treating her as a personal maid of the brother even though they know she is doing bad at school and would need tuition instead of dedicating her time in the kitchen.
Then another disturbing point, the brother is in love with his sister... Since when it's ok to think that because they are not related by blood is ok to droll behind your adoptive sister? Sounds like, in every family with an adoptive daughter, the brother should be allowed to chase his own sister, because hey, they are not related by blood... Are you serious?
The message that this drama is passing down to youngsters is terrible. Bullying, incest, harassment, there's nothing cute or fluffy to be seen here. And I didn't got to see the bitchy second FL in action yet. Can only imagine it will only get worse.
Ah, and to conclude, the acting is plain boring and at times just terrible.