Makoto has been admiring a girl he has seen on the train. That girl is Kotonoha Katsura, and he even managed to take a photo of her with his cell phone. Due to new seating in his class, he ends up next to Sekai Saionji, a nosy girl but sweet and sincere. As she snoops for his cell phone while talking to him, she discovers his crush and vows to help him until Kotonoha agrees to go out with him. When Sekai finally gets them together, she realizes her own feelings after finding out that the person Kotonoha liked was, in fact, Makoto. While waiting for her train next to Makoto, who was waiting for Kotonoha, she has him talking about how he can repay her for all of her help. Before leaving for her train, she kisses him and cries when she boards the way home. Kotonoha happily arrives for her date with Makoto shortly after. With all three main characters carrying different expressions on their faces, the story begins.
(taken and edited from wiki)

Picture	Real Name	Description
	Makoto Ito	He attends Sakakino Gakuen and is in class 3, first year. His parents are divorced and he lives together with his mother in an upperscale apartment. Throughout the story, he is indecisive and unable to decide between Sekai and Kotonoha.
	Kotonoha Katsura	In year 1, class 4. She takes the same train as Makoto and becomes his girlfriend by the second episode. Despite her busty figure, she is quiet and has a respectable nature, but is also somewhat frightened of boys. She is disliked by the girls in the student council. Her family is rich, with both of her parents working, and lives in a large house away from the city.
	Sekai Saionji	Also in year 1, class 3, she is Makoto's classmate. Sitting next to him in class, she sees the picture that Makoto has secretly taken of Kotonoha on his mobile phone. She then helps him get close to Kotonoha despite harbouring strong feelings for him, kissing him at a train station near the end of episode 1. Even though she is good-natured her emotions overwhelm her in many situations, causing her to give in to Makoto and betray Kotonoha. She lives with her mother in an apartment.
	Setsuna Kiyoura	Also in year 1, class 3, Setsuna is a member of the class committee and is childhood friends with Sekai. Their mothers are good friends working at the same company. She is the main heroine in Summer Days. Although silent-looking and almost emotionless, she is conscious about the small size of her breasts, especially in comparison with Kotonoha and Sekai.
	Nanami Kanroji	A friend of Sekai's that used to go to the same school with her. Nanami is in year 1, class 3. She was offered admission to the school based on her special athletic talents. Her boyfriend is also her senior and is in the school's basketball club. Her boyfriend is a hardcore otaku.
	Hikari Kuroda	One of Sekai's friend who is in the same class with Makoto and Sekai. She dislikes Makoto whom she believe is going out with Sekai since the beginning of the story. She also has a crush on Taisuke.
	Otome Kato	She is in year 1 class 4 of Sakakino Gakuen, and one of Makoto's friends since junior high. She's in girl's basketball team, and also is the head of the group of girls who bullies Kotonoha.
	Kokoro Katsura	Kotonoha's younger sister. Unlike her shy older sister, she is very talkative, full of curiosity, and likes to tease Kotonoha around, but she actually worries about Kotonoha a lot. She often wants to play with Makoto during his visits at her house.
	Taisuke Sawanaga	He is one of Makoto's friends since junior high, and is in the same class as Makoto.