Sister Princess contains anime episodes 1-26 of Season 1.

Wataru Minakami was at the top of his class in middle school and had a pretty comfy life in Tokyo. But, when he unexpectedly fails his only high school entrance exam because of a computer glitch, his life is suddenly thrown into utter chaos! Jeeves, Wataru’s trusted butler, sends him off to attend school on a mysterious island. Upon his arrival, Wataru encounters many friendly, cute girls.

This isn’t a problem until he finds out they are all his sisters! For most kids, adjusting to life at a new school in a different town is tough enough. But for Wataru Minakami, high school will be the easy part!