Doushin: Same Heart (同心～三姉妹のエチュード～, Dōshin ~ Sanshimai no Ecūdo) is a dating sim/eroge originally developed by Crowd, and translated by Peach Princess into English. The game has a multiple-choice, "zapping" interface with a lot of CG.
In this game, you take the role of one of the three Suruga sisters: Ryoko, Maki and Miho. Each one has their own storyline, however their storyline are intertwined as the sisters have a secret they can't tell anyone: due to an unexplained physical phenomenon, a sensation shared by one Suruga sister will be felt by her two sisters, no matter where they are.
The player takes the role of one of the three sisters. The areas of exploration vary depending upon who one plays, though certain areas, such as the house and main commercial street are the same for all three. Depending upon the character one is playing, one's role varies. To get a good ending one must pay attention to all the clues and at time one must use the zapping mechanism of the game. One can turn on a reference that gives one a letter grade as to how close one is to a good ending as well.
Zapping allows you to move from one girl to another. Sometimes you can switch between any of them and sometimes you are limited for various reasons. Switching is supposed to be conversations started during that timeslot, though sometimes you can switch 5 minutes to the past/future. Zapping is not only useful to get all the scenes, but changes the storyline and is necessary to get all the endings. However, using this may block other encounters later on so you have to be careful how you use this.
The Suruga Sisters
Ryoko is the oldest of the three, age 23. She works as a company office lady along with Misaki Suou, her office lady friend, and feels responsibility for her younger sisters because it was up to her to raise her them when the their parents died. She's popular with the male employees at her company and as the game progesses misfortune follows her in the work environment and you have to find a way out.
Maki is the middle of the two sisters, age 20, and full of energy. She goes to college with her questionable boyfriend, Ippei Takebayashi, and a foreign exchange student classmate Chamsi "Cham" Bene. She is the tennis club's top player and all three are members as well as a self-proclaimed arch-rival, Arisu Kagurazaka. The storyline progresses through the game as she has to deal with her college life.
The youngest of the three, Miho complains about looking younger than she is despite being in highschool. She is a bookworm and has only one friend at school, her classmate Kei Satonaka. Miho has a secret crush on another one of her classmates, Yusuke "Nasshi" Nashimoto, whom only Kei knows about. The story follows her high school life as turmoil erupts between her and Kei over the latter's crush.
Main Supporting Characters
Chief of the General Affaris office, Kazuhiro, age 29, is a capable manager, but has a tendency for wandering fingers when it comes to female employees. He is a charming man with a powerful will. As the story progresses he becomes involved with Ryoko.
Best friend of Ryoko's and another Office Lady at the same branch. She comes from a well-off family and has a pure heart. She tries to do everything she can to help Ryoko, even though the latter tries to keep her distanced to keep her from trouble.
Ippei, known as Ippei-chan by Maki despite being a male, hangs around with Maki. The relationship is questionable boyfriend/girlfriend. Ippei is cheerful and full of energy just like Maki, but he is also very laid back as well. He is a part of the Tennis Club, and according to Maki could be better than her, but he ditches it most of the time because he doesn't like it. He is also friends with Cham.
Chamsi "Cham" Bene
A foreign exchange student from Thailand. Maki and Ippei appear to be her only friends, although Arisu seems to tolerate her and even get along with her at times. She is quite clueless and has an unusual sense of taste in food compared to her friends. Because of her cluelessness, Maki feels like a guardian or older sister and tries to protect Cham.
President of the Tennis Club, Arisu comes from a rich family and is very competitive. She is Maki's self-proclaimed arch-rival, though she constantly falls short of Maki, according to the latter because she gets worked up to much. The rivalry includes everything from Tennis playing to seeing who can eat the fastest, or retaking classes just to beat Maki in that session.
Kei is 18 yrs old and has a crush on Hashiba-senpai. She is Miho's classmate and best friend and wants to see romance bloom between Miho and Nasshi, to the point of trying to force them together at times, much to Miho's dislike. As the story progresses, she thinks Miho is trying to steal Hashiba-senpai from her and becomes jealous.
Yusuke "Nasshi" Nashimoto
Yusuke Nashimoto, nicknamed by Kei as Nasshi, is quiet and reserved. He is completely oblivious to Miho's feelings for him. He is classmates with both Miho and Kei. He is friends with both of them and tries to help them out when they need it.
Hashiba is a senior in Miho's school. He is the heart-throb because he's a good athlete and every woman wants him, with Kei being no exception. He has a tendency to use women as objects though. As the game progresses, Miho, Kei and Hashiba get involved in a triangular relationship and Kei becomes jealous of Miho.
The zapping feature in Doushin: Same Heart has had some mixed results. On the one hand, it clearly showed a new innovative twist to the tried and tested visual novel format. However, there were concerns that it left the players confused because of all the possibilities and how switching can affect things.