W~Wish~ (pronounced Double Wish) is about a boy, Junna Tōno (遠野潤和, Tōno Junna), who has a twin sister named Senna Tōno (遠野泉奈, Tōno Senna). He is an Ordinary High-School Student at Sakurahama Private High School happily living with his twin. However, in the past, a traffic accident deprived him of his parents and his memory. Junna survived the accident and since then, he lived only with his sister alone in a house. Senna and Junna support and rely on each other, and due to this Senna is very fond of her Onii-chan.
Junna's present life with Senna at the same high school is so pleasant that he can forget his severe past. However, Junna begins to recall the memories he lost in the accident. He enjoys the happy and pleasant days, but he is tossed by his past, his present, and his future.
Then one day a girl named Haruhi Inohara (井ノ原春陽, Inohara Haruhi) transfers, claiming to be his childhood friend but later to be his younger sister who he suddenly remembers. Who is his actual sister, Haruhi or Senna? What is the truth hidden in his memory?
W~Wish~ provides examples of:
- Bittersweet Ending : Senna wished that she continue to exist as Junna's sister, Junna wished for Senna and Haruhi to exist, and Haruhi wished to be Junna's childhood friend. To compromise all three, Haruhi becomes Junna's childhood friend while Junna's parents become pregnant with a new child that they plan to name Senna.
- Brother–Sister Incest: Played with; Haruhi definitely is in love with Junna and the entire reason she wishes to become Junna's childhood friend is because you can't marry your brother. Her wish is granted making her no longer his sister. It doesn't help that Senna also gets visibly jealous of girls who get close to her brother.
- Don't Split Us Up: Senna was supposed to be Junna's twin sister in the real world, but since she died at childbirth she doesn't exist. Should Junna wish to return to the real world, Senna would disappear.
- Everyone Is Related: It's eventually revealed that Haruhi is actually Junna's sister. Which means all three are siblings.
- Hadaka Apron: Haruhi wears one in the specials, as does Tomo.
- Relative Error: Senna's attachment to Junna can easily show this.
- The Reveal: Haruhi is actually Junna's sister and Senna doesn't exist.