If you suddenly found out you had 12 sisters...and they all loved you so much, what would you do?
In this sweet anime, a boy named Wataru comes to a place called Promised Island, after he fails an exam, and is sent to school there. While there, and depressed about it, he meets 12 girls (each in groups of 4) and they all claim to be his sister! He does not know how to feel about that, but goes along with it and ends up living with him. There comes a "13th" sister, but she ends up being a spy to get him back home. Each of the sisters has a very different personality, but loveable nonetheless. At first Wataru seems to try very hard to leave the island, but each day he spends with his sisters gets him more and more attatched. The drama comes later on in the series. There is also a mysterious little girl that you see occasionally..though never her face. No one knows who she is..though at times she seems to feel all the emotions of all the sisters at once.
If you like shoujo anime, you'll love Sister Princess!