Say "I love you".

We are introduced to 16-year-old Mei Tachibana, who, after suffering a traumatic experience in making friends, decides to ditch making friends altogether during high school. She catches the attention of Yamato Kurosawa, the most popular boy among the girls in their high school, and wasted no time making friends with her, even giving her his number, despite the refusals, and even accidentally kicking him when she thought Yamato lifted her skirt a bit (it was just his pervy friend Kenji Nakanishi), earning the ire of Yamato's girl followers. She tried putting it at the back of her mind, until, one night, when a stalker followed her on the way home from her part-time job. Deciding to hide in a convenience store, she tried calling home, but no one answers. She calls Yamato, who rushes to the scene despite being at karaoke with friends at that time. Yamato wards the stalker away by pretending to be Mei's boyfriend...complete with the "I love you" phrase and what eventually became Mei's first kiss.

Ever since that rescue by Yamato, Mei started having dreams about him being her protector. Later on she gets to befriend Asami Oikawa, who idolizes Yamato. It was from her that Mei heard rumors about Yamato kissing every cute girl in their school save for one girl named Arai, rumored to be his girlfriend. For this she refuses Yamato's invitation to karaoke. However, because Asami has big breasts, she is being bullied at school, and Mei even stands up for her, at the cost of her cheek. Asami accompanies her to the clinic, though Yamato has bandaged it up prior. Kenji, who is heading for the clinic after being hit by a soccer ball in the face, catches the two bully girls inside the school clinic picking on Asami and defends her, though a little misunderstanding about her breasts and his bleeding nose made her run away. With some encouragement from Mei, Kenji eventually confesses his feelings for her. Meanwhile, bothered by the rumors, Mei secretly follows Yamato at the karaoke (where Arai is flirting with him in full throttle), and eventually feels how Yamato kisses the people he really cares for. When Mei says that she loves him, Yamato kisses her "for real."

Yamato tags along as Mei intends to visit the parlor to have her hair cut, eventually becoming a date. On the way they meet Aiko Muto, along with her boyfriend Masashi Tachikawa, and eventually invites the two to a bowling alley. Aiko, who has a crush on Yamato after finding out her ex-boyfriend cheated on her, wonders what did he see in Mei, who looks not interested in him. When the two girls are alone Aiko bluffs Mei into leaving him alone, but it was in vain as Yamato followed Mei on the way out. Yamato momentarily loses Mei, but knew where to find her. Eventually he shows Mei his middle school, where he sheds light on his past, about not caring about anybody else as a middle schooler, even with his best friend who was being bullied. He says it's him who is having a hard time blending with others. For this Mei, who herself needs to trust others, tells him to trust others, else he will lose friends. She decided not to go to the parlor anymore, after learning that trusting others makes people learn about others. Meanwhile, despite Aiko spending some time with Masashi in a love hotel, she has not given up on Yamato, yet.

Mei has attracted the attention of one Kakeru Hayakawa, a guy known to have slept with many other girls, including Aiko. He then wastes no time in asking Yamato if he can hook him up with Mei for lunch with him. Yamato is unaware, though, that Kakeru has other designs for Mei, and, when Yamato was distracted by a phone call, he tried to convince her to be his girlfriend. But Mei sensed his motives and leaves him alone in an instant. Yamato learns of what happened, and when Kakeru starts badmouthing Mei, he punched him, saying she's his girlfriend. Kakeru tells Aiko about this the other day, but, despite being surprised about this development, she instead scolds him, that he will not be like Yamato. Mei appears to them, adding her impression of Kakeru. As he leaves in disgust, Mei, while recognizing Aiko's sacrifices, states that she is not giving Yamato up. Later, Yamato catches up with Mei, and confesses to her that he did sleep with Aiko, but only because back then she was heartbroken and lost. But he swears that he will never do it again with any girl, except if it is Mei.

Yamato has invited Mei to his house; the pressure is almost overwhelming. Yamato’s little sister doesn’t pull punches when she sizes up Mei for the first time.

A new girl has transferred into Toumei, the rising idol Megu-tan and she has set her eyes on Yamato.

Yamato's new fame as a model is widening the rift between him and Mei. An offer to continue modeling with Megu-tan might be the breaking point in their relationship.

Mei is trying to be strong, but this new feeling she is having is starting tearing her apart. So young and new to love, it will take the help of her friends to make everything right.

Megumi was surprised to hear from Yamato that he is quitting the modeling business because it makes Mei sad. It's because of this that Megumi starts to ignore Mei with a bit of a hatred, while wondering why Yamato chose Mei over her. However, just as Yamato gets to meet Mei's mother, and, eventually, as things start to look better between the two, Kai doubles his efforts towards Mei, but he, through that key trinket, eventually knows she has a boyfriend, which he later knew to be Yamato when he returned to school. Mei gets to know of Kai's plans to gain revenge against his former tormentors, so she gives him some advice. With his mission of gaining revenge against his bullies looking bleak, Kai, as he declares in front of Yamato, fully turns to another mission: winning Mei's heart.

After listening to Mei’s, Kai’s, and Asami conversation about Land, she hatches a new plan to drive a wedge between Mei and Yamato.

Yamato is planning a trip for him and Mei to Land, but somebody is trying hard to sabotage it. Megumi begins to unravel when her “friends” and popularity start to drop.

An emotionally fallen Megumi must pick herself up and become true to herself. Mei is given some motherly advice on her relationship with Yamato.

Yamato is sick and under the care of his over protective sister, a timid Mei wants to visit but can't find the courage.