Straight Up Sister-Zoned

For Nanoreno 17 Shuna is the privileged heiress of a ridiculously rich family. What she lacked in attention, her parents made up with money. LOADS of it. The only person who didn't always treat her like some soon-to-melt snowflake was Atsuya, the "nii-san" who lives acrossthe street... At first, she followed him everywhere out of admiration... which as they grew up, turned into a one-sided adoration. There's this one LITTLE problem though: He sees her as a little sister... nothing more, nothing less... Oh, but she'd wait this out! He'd soon realize her worth as a potential love interest. If not today, maybe in a decade or two? However, when she gets wind that her parents are announcing her engagement on her 18th birthday, she decides to actively pursue this fake older brother of hers. Will she steal his heart away? Or will she stay the 'little sister' character and concede to fate? You decide!~