You know, there's no opportunity for the all-important slowly-getting-closer-together, what-is-this-feeling, what's-our-relationships stage if the girl just comes in already at LUV YOU ONIICHAN PAY ATTENTION TO ME mode. What's the point of the pseudo-incestuous taboo dynamic if it's literally introductions and she already wants to fuck? Like, first of all, who are you?
Not that I'm a connoisseur of step-sibling romance in fiction (lol), but this is seriously all wrong. Where's the awkward distance and the desire to get closer? Where are the shared moments of familial bonding? Where are the subtle sexual tension and guilt? Where's the delicate feeling of budding love? Where is *everything*?