Sister Princess (Original Japanese)

Wataru, the top student at his elite school, is in a depressive mood after failing to pass the entrance exam to a prestigious high school because of a computer glitch.

Wataru thinks this must all be a dream, because “it can’t be true!” He is “Big Brother” to Karen, “Dear Brother” to Sakuya, “Brother” to young Kaho, and “Bro Bro” to younger Hinako. Despite their affection and charm he still investigates, vainly, for any way off the island and out of his surreal dream.

Wataru and his sisters attend their first day of school, but Wataru is feeling the pressure to watch over them. Everywhere he goes at least one of his sisters follows him wanting attention, and Wataru starts to feel overloaded.

Wataru helps Hinako, his youngest sister, search for a teddy bear that she saw in a dream she had. They go all around town in every store but cannot find the exact right bear.

The sisters are beginning to be jealous about the numerous e-mail messages Wataru is exchanging, so they each get RinRin (the invention sister) to make them phones that can send e-mail so they can exchange mail with Wataru.

Wataru and 12 sisters plus Mami all see a contest to win a special prize and decide to try and win it by putting on a play Yamata wrote called the 12 gentle princesses.

Simple fun with the laundry turned into play wedding dresses as the sisters dress themselves up as brides. It is first hinted in this episode that Wataru will need to make some kind of choice between the 12 girls.

Wataru spends a day with Marie, a gentle sister in chronic ill health. Marie becomes sick because of a downpour. Wataru vows to stay with her forever, and after a day or two of care and encouragement from “Brother Mine”, Marie is completely better.

Wataru spends his initial summer days with his sisters. They all go out to buy swimsuits and all the sisters each get one. Everyone, including creepy Yamada, joins in to clean the pool so they can splash around. Later, Wataru admits he does not know how to swim and decides to learn how.

Athletic and dauntless sister Mamoru trains her “Big Bro” Wataru to swim. Despite her unflagging support and his best efforts, he decides to give up, but when he thinks delicate sister Aria is floundering dangerously in the pool, his race to rescue her enables him to learn the doggy paddle.

Wataru and his sisters set out in on an underwater tour in a submarine single-handedly constructed by Rin Rin. At first, the ocean is beautiful and everything is great, but a storm comes in and the submarine starts leaking. Wataru tries to patch it up, but he fails and everyone is scattered and ship-wreaked, leaving Wataru and Mami alone.

All 12 sisters plus Mami and Wataru are ship-wreaked on an unknown island together, where they find a large and well-stocked beach house. They decide to live there while they try to figure out where they are and how to get home, and have some fun while they're at it.

Wataru reminisces his time with his sisters so far. Just a recap episode, except for the very, very end where we get a glimpse of the elusive and mysterious little girl in the yellow hat who has appeared in the credits of every episode.

Wataru, feeling that he does not do enough for everyone, tells the sisters that if they have a request, he will grant it. Karen's request to have a lightbulb changed that illuminates a painting ends up with the two spending their time together.

The wind blows away Aria's ribbon (which her Mon Frère Wataru gave her). She is then accompanied by a strange old man to help her find it.

Kaho continues to fumble on her cheerleading routine. She however tries her best to cheer for her brother in the autumn sports festival, and Wataru needs all the help he can get, being a nerd who is bad at sports.

Haruka, often shy around her Beloved Brother Wataru, tells him that her most fulfilling dream would be for him to take her out dancing at the ball; Wataru initially hedges but realizes how much it would mean to her, and agrees to take her if she will be content with any laughter his poor skills might bring upon them.

Wataru is having a dream of Chikage, and when he wakes up, he sees his body still asleep on the bed. Freaking out, Wataru runs through walls trying to find someone who can see him, but no one can except for Chikage.

Shirayuki prepares bentos for everyone for their school lunches, and Yamada is jealous so he tells Shirayuki that Wataru is not getting enough nutrition in the hope that she will make too much and he'll get the leftovers. Yamada's plan works too well and she starts making too much for every meal until Wataru tells her that they need smaller portions.

Wataru celebrates Christmas with his sisters. All 13 sisters prepare a christmas present for Wataru while he goes out shopping for one for them.

Rin Rin introduces her latest invention to Bro Wataru—a robot version of herself. She based it on all the sisters so that it would cook and clean and be graceful and strong so it could help Wataru with whatever he needs. RinRin reveals that she wants to study robotics in America, and that when she leaves, she wants there to be someone who can help Wataru out.

Everyone notices that they each have an item missing, and Yotsuba decides that she will discover the culprit using her detective skills. While fixing dinner, Mami accidentally breaks a leg off of the music box, but hides the fact by making it look ok.

Wataru's friend Akio arrives at the island for a visit and all the sisters like him except for Mami, who hides and acts nervous.

Akio tells Wataru that he had actually passed the exams. Wataru is not sure how he feels about this, and though Akio is pushing him to return to Tokyo, Wataru wants to decide for himself.

The sisters' house feels empty as they miss their brother and anticipate his return with all their hearts. Meanwhile, Wataru is back in Tokyo with Akio and is ready to forget his memories in Promised Island when Mami shows up, begging him to return.