You weren’t my sister, but my fiancée!?

Humanity, love your little sister.
I miss the time when her younger sister Kana was fond of me.
Takashi Shiina lamented the current days when he was often ignored.
One day, his parents cut out a shocking story.
Surprisingly, he wasn’t his real son… but he was his sister Kana’s fiancée! ?
The definitive version of Reiwa’s younger sister manga!