Ah yes, this manga is like Sono Bisque Doll wa Koi o Suru with step-sister girlfriend theme
Actually my aunts call my dad brother 😂I do wish y'all would retain "onii-chan" because it just hits completely different than the more plebeian "brother" (which no English-speaker would ever use as a form of address in the first place).
It's called gap moe you uncultured- cough coughWhy do they keep repeating the "I'm the only one who sees her like this" bit lol, making the MC try to flex on the reader makes no sense