Responses

this could just be me but i think the little brother may already know (and this is completely based off what i would do) because the MC introduced himself as his olders sister's "younger sister" and i know i personally would ask the older sister if she had a younger sister to make sure i'm not talking to some creep. but this is complete baseless
The 3rd chapter is the cutest shit ever I hope the brother doesn’t mind the mc is actually a guy