- Designated Villain: Akio doesn't really do much at all, let alone anything villainous, but he's treated as such after the Wham Episode because he separates Wataru from his sisters.
- Ensemble Dark Horse:
- Mami is pretty popular.
- Michael, Marie's dog, is adored by everyone.
- Ho Yay: Between Wataru's lighting up upon receiving Akio's e-mail and Akio 'convincing' Wataru to return with him, not to mention his reaction when Wataru decides to stay on the Island, Akio's status as the Gay Option is apparent.
- Incest Yay Shipping: Given the nature of the work, this is not surprising. Fans pretty much ship Wataru with almost every one of his sisters, even the youngest...
- "Seinfeld" Is Unfunny: Due to being one of the earliest harem stories in the anime industry, as well as being one that would be a major basis for things like the Little Sister Heroine boom in the years to follow, it definitely comes across as a massive Cliché Storm that can't really hold up to many of the newer series out there.
- Tastes Like Diabetes: The story takes place on a bright and sunny island where twelve cute girls basically worship their brother, who quickly develops Big Brother Instinct for all of them. This series feels like your veins are being repeatedly jabbed with a needle full of liquid sugar.
- The Scrappy: Taro Yamada, the most annoying character of the anime series, whose appearance in nearly every episode amount to nothing.
YMMV / Sister Princess