It's a breath of fresh-ish air. Because most authors would just go for cliche brocon imouto for fetish reason. She's simply a little sister.Pleasantly surprised that the little sister isn't just another "little sister" archetype character, especially in terms of design.
shiranui-san would truly make perfect future wife for MC
She's an aunt, but she doesn't like being called that. Makes her feel older. It was in one of the previous chaptersThe nurse calls herself onee-san. Is she actually MC's older sister? She doesn't have the signature eye-bags unlike the two siblings.