乃木坂春香の秘密

After Yūto Ayase returns an anime magazine to the school library, he accidentally runs into the most popular girl in school, Haruka Nogizaka, and discovers her secret that she is an anime and manga otaku which greatly distresses her. Haruka starts avoiding Yūto at all costs which causes others around them to blame Yūto for doing something bad to her. Eventually, Yūto finds Haruka on the school roof where he explains that he will not tell anyone about her secret hobbies if she does not want anyone else to know. This makes Haruka very relieved and happy that if anyone had to find it that it was Yūto.

Yūto and Haruka start spending more time together, such as walking to school together, which causes their peers to get annoyed that Haruka would be hanging out with someone like Yūto. Haruka asks Yūto to accompany her to Akihabara on Sunday and he agrees. The two spend most of the day going from store to store looking at the goods but not buying anything, though Haruka wastes some money on a toy vending machine. Yūto and Haruka even go to a maid café for lunch where Haruka is dressed in a pink maid uniform and gets her picture taken with Yūto. At the end of the day, they discover the handheld gaming console Haruka had intended to buy was sold out for now. This distresses Haruka, but Yūto cheers her up later by assuring her that he had a good time today with her.

The day before a test, Yūto comes over to Haruka's mansion and meets her younger sister Mika and two of her maids, Hazuki and Nanami. The next day at school, a guy bumps into Haruka which causes her bag to go flying which also exposes the Comiket catalog she had. Yūto manages to make everyone believe the catalog is actually his and Haruka only picked it up, though after this Haruka does not come to school for three days. He goes to see her where he finds out from Mika how her secret was exposed during middle school and she had to transfer schools due to being isolated from her peers. Yūto assures her that he will never leave her which relieves her so much that the next day she affirms after a short conflict that the catalog is actually hers.

Yūto, Haruka, Mika and Nanami become increasingly worried about Hazuki's attempt to distance herself from the family and thus decide to follow her on a shopping trip, meeting up with various familiar faces like Yūto's otaku friend Nobunaga, Yūto's sister Ruko and their teacher Yukari. Mika and Nanami eventually becomes distracted in buying lingerie, leaving Yūto and Haruka to the job and almost came to a conclusion that Hazuki was about to get married and quit her job. Before going home, they had a misunderstanding with a bridal shop where they are thought to be customers and were given a chance to take a portrait together with Yūto wearing a tuxedo and Haruka in a wedding dress. That night, Hazuki, much to everyone's relief, explains that she is not quitting, but was just going to a hardware store, which was located above the bridal shop, to fix her chainsaw.

The girl Yūto already bumped into twice turns out to be Shiina Amamiya, the new transfer student into his class. The school swimming tournament is coming the following week, but while Shiina can do an arrange of other skills, swimming is not one of her strong points, so Yūto and Haruka help her prepare in the school pool, but Yūto's sister, and Haruka's sister and maids come along too. At the tournament, Shiina gets a leg cramp during the race and Yūto jumps in to save her, and he takes her to the infirmary. She was not seriously injured, and was more shocked than anything else; Yūto reassures her that she tried her hardest, and that is what matters.

Yūto and Haruka attend the summer Comiket convention together, but since it is the first time for both of them, they underestimate the massive scale and hoards of people who attend. Mika, Hazuki, and Nanami tag along in disguise and help Haruka obtain a dōjinshi she wanted, and to get her out of trouble when people started taking pictures of her. Yūto and Haruka grow closer throughout the day, but after he leaves her at her house, Yūto is asked if he and Haruka were followed by anyone at the convention, but he says he did not see anyone like that. That night, a frantic Haruka unexpectedly shows up at Yūto's house.

Haruka reveals that her father, Gentō, found out about her hobby and went on a rage, confiscating her anime goods and she leaves with her first issue of Innocent Smile. She hides in Yūto's house alongside Hazuki, while Mika prepares a 'secret weapon' to counter their father. Unfortunately, the next morning, Gentō arrives and assaults the Ayase house with his personal squad, the Hell Hounds. Haruka refuses to go home, and Yūto openly protests about the ostracization towards anime-otaku and disapproval towards Haruka's hobby. Eventually, Mika and Nanami arrives with their 'secret weapon': Haruka's mother Akiho, who verbally and mentally brings down Gentō and makes him leave after apologizing for his outburst.

Mika becomes angry when she realizes that the relationship between Yūto and her sister is not progressing as well as she expected, so she forces Yūto out on a date with her to teach him tips to get in the right mood with Haruka. During their date, they go to a café, and catch a movie before running into Shiina, which makes Mika jealous. Mika drags Yūto to a kimono shop and the two are outfitted with brand-new kimonos before heading to the summer festival and watching the fireworks with Haruka, Hazuki, and Nanami who find them. Once school starts again, Shiina volunteers to be one of the organizing members for her class' participation in the upcoming cultural festival, and Yūto gets dragged in to work with her.

Yūto's class decides to do a cosplay café for the school festival, for which Yūto asks Haruka to go to Akihabara with him to see examples of cosplay costumes. Unknown to Yūto, Haruka had previously made a promise to her father to meet his client, however she decides to go with Yūto to Akihabara instead. Gentō becomes furious when he finds out and goes and finds them, but Akiho comes just in time to save them again. Haruka makes cookies and goes to give them to Yūto, but is shocked when she finds Yūto on top of Shiina at school.

Haruka quickly leaves after seeing Yūto on top of Shiina, but when Yūto tries to explain the situation to her, Haruka says she understands, but ends up running back home. The next day during the school festival, Yūto finds Haruka to have apparently forgotten about yesterday, though Shiina is not so sure. Yūto confronts Haruka about yesterday again, but she tells him she does not want to hear what he has to say and runs off. Yūto runs into Hazuki as he is searching for Haruka, and she gives him so advice on how to move forward with Haruka. With Hazuki's help, Yūto finds Haruka behind the gym where he apologizes for yesterday and assures her that he will not leave her. Afterwards, the two dance by the tune of the music box Yūto gave her previously as Nanami, Mika, and Hazuki watch from the bushes.

Mika calls Yūto late at night to invite him to Haruka's birthday party on the evening of October 20. On the day of the celebration, Yūto goes to Akihabara to buy a gift and bumps into Nobunaga. After buying the gift, Yūto goes home and is fetched by Hazuki and Nanami to be taken to the party venue on an island far away together with Ruko and Yukari. On the island, Yūto meets up with Mika and Haruka. After meeting some of the guests, Yūto starts feeling insecure about his gift and social status.

The party has started and Yūto is dragged inside the party hall by Mika. While waiting for Yūto's turn to present his gift, he again bumps into one of the guests and his gift is ridiculed. Yūto becomes insecure and is about to leave the party hall when an old man, who happens to be Haruka’s grandfather, helps Yūto regain back his confidence. Yūto runs back to Haruka and presents his gift. After the party, Yūto is with Haruka in her room, and Yūto then realizes that he was the one who gave the copy of the first issue of Innocent Smile to Haruka when they were kids.