I thought the premise was interesting so I gave this a try but I'm disappointed. The art is very hit and miss and the writing just feels bad, such generic characters that say or do things that don't make much sense at times. Narumi acts like he has a terrible home situation and that he and Kazemiya are the same so he understands but it's literally not even close to the same situation, she's dealing with genuine trauma from an awful family and he just feels awkward at home just because his stepsister is good at everything and he feels like it makes him look bad, sure he's a teen but that's laughably childish. He even acts shocked that Kazemiya has friend's saying 'you of all people has friend's?' like bruh how dumb is this guy, she's a pretty girl that just has some rumours around her, yet he somehow thinks she should be a complete loner. Even for a manga like this the pacing is off too, they almost instantly start feeling strongly about each other despite not much happening other than a couple of conversations. Anyway, are these issues just the manga or is there a light novel worth reading?
Their situations aren't the same? Yes AND no. He has a terrible father who was just like her mother. He is more fortunate than her, because he has a family (step family). But so does she, she has her sister.
In his case he was driven to trauma due to his father and his family isn't the helping stone, because his sister and partially mother keep opening the wound. Sadly his trauma cannot be healed by his family, since he is already in this mental state. (It's like depression there are small chances to outgrow it but in most cases you need outside help, the causer of the problem rarely can be the absolver of the problem)
Her situation is indeed objectively worse, because she is forced to live with her tormentor and the same situation as MC, FMC has a sister that is good to her but her existence keeps opening the wound.
Not to mention if you read up to chapter 9, you will understand that he is concious about his situation and actually he supports her emotionally more than she, so it balances out. She on the other hand helped him to accept his family more, his problem might seem as a smaller hurdle (and it is) but it isn't to easy to solve without outside help.