Haruka Nogizaka's Secret: Purezza

Yūto has lately been watching one of Haruka's favorite anime, Nocturne Girl's School Lacrosse Club. Yūto and Haruka along with several others are invited by Shiina to go to a hot spring in the mountains. Haruka is especially excited since this is her first trip with friends, due to having her hobby of watching anime being exposed in junior high school. Haruka's maids and her younger sister Mika also come along, as well as Yūto elder sister Ruko and Yūto's teacher Yukari Kamishiro. When everyone is out in town, Yūto finally manages to tell Haruka about an event close by to meet the voice actress of the lead character from Nocturne Girl's School Lacrosse Club. Nobunaga runs into Yūto and gives him two tickets for the event, as he did not know he had to buy them beforehand. Haruka enjoys the event and treasures it as a precious memory.

Yūto and Haruka begin making a dōjinshi together, though Haruka's skill in drawing is still lacking. Nobunaga asks Yūto to cover for him selling dōjinshi for one of his friends' dōjin circles at an upcoming event for Nocturne Girl's School Lacrosse Club. Yūto asks Haruka to accompany him, who is overjoyed at the prospect of helping out an already established circle. Yūto and Haruka continue their work on Haruka's illustration book of the Nocturne Girl's School Lacrosse Club lead character Haruna, though the day of the event Haruka's book is not selling. Nobunaga gives Yūto some advice, telling him that half the enjoyment is actually making the dōjinshi and Yūto realizes there are more important things that the book selling or not. Yūto goes back to Haruka and starts promoting Haruka's book, and eventually three people end up buying it.

After finding out that Haruka is working to get him a Christmas present, Yūto decides to apply for a well-paying job as a part-time butler. He gets the job, but he must unfortunately serve the selfish and demanding Tōka Tennōji, a girl one year his junior, whose previous part-time butlers quit after a day or less at her command. Yūto has his work cut out for him, but soon finds that there is more to Tōka's situation than he initially realized. Through kindness and hard work he manages to gain Tōka's favor, but a certain situation results in damages that cost him nearly all of his pay.

The Nogizaka family visits Yuuto's house for a Christmas party. However, the party is cut short when Yuuto faints, having worked himself to exhaustion to buy Haruka a Christmas present. When Yūto regains consciousness, Haruka declares that she will stay by his side in order to nurse him back to health, under the guidance of a very questionable guidebook prepared by Mika. To preserve the Christmas spirit in spite of Yūto's poor health, Haruka decorates his yard with Christmas lights, and presents him with a Christmas present. He in turn presents her with his present: a ring called "Clair de lune" which, at Haruka's request, he places on her ring finger. The two thus share another precious memory together.

Yuuto is invited to the annual encounter of maids and butlers due to his one week job at the Tennouji household. Yuuto is introduced to the rest of the Nogizaka family's maids and enjoys the party alongside Alice, until the arrival of Shute Sutherland, the same rich boy who caused him trouble during Haruka's birthday party, and because of it was ordered by his father to work as a butler for a while as a lesson in humility. After having his suit accidentally dirtied by Alice, Shute shouts at her and states how the butlers and maids at the party are inferior beings. However, Yuuto stands to protect Alice, and with Shute's father's approval, he and his lackeys are given the proper punishment by the members of the gathering. Yuuto is complimented by the other guests, and Alice mutters some words of thanks to him.

It is New Years Day and everyone has gone to visit the local shrine together. Although Haruka and Yūto were hoping to spend some time together, it is not long before Haruka's admirers, who are hostile to Yūto, whisk her away. Later, after both Haruka and Yūto receive encouraging fortunes (courtesy of Mika, Hazuki and Nanami—working as shrine miko), Haruka manages to get rid of those admirers. Haruka and Yūto bump into a mysterious girl, who is running away from someone. Later, Haruka takes Yūto to the cape where her parents shared their first kiss, so they can watch the sunrise together.

During the New Years break, Shiina expects something good from the fortune she received at the shrine, and coincidentally runs into Yūto on the street. Her hairpin gets knocked off into the river and Yūto goes in to retrieve it; as a thank you gift, Shiina prepares some cooked squid, but hurts her foot in the process. Mai and Ryouko, two of Shiina's friends, and Yūto come to pay her a visit, during which Yūto gives the three girls an unforgettable massage, a "punishment" for losing a game of old maid. Later on, Yūto and the others leave for the day, but Yūto comes back because he was worried about Shiina. Yūto helps her by preparing dinner, and the two spend the rest of the night having fun together. On the day Shiina returns to school from the holidays, she is cheerful, and gets giddier with joy when she meets Yūto, even with Haruka near him.

Yūto visits Mika's junior high school—an all-girls' school—upon her invitation. Mika introduces him to the rest of the girls in her class. He was surprised to know that Mika was a popular girl at school. She is a class president and a school idol, pretty much like her sister Haruka. After their meeting, Yūto decides to go and see Mika's stage play. After the stage play, both Yūto and Mika are accidentally locked up in the stage room. Luckily in the end, Mika's maids find them.

Haruka and Yūto are finally having some time for themselves. They go to the fair to have some fun together. There, Milan Himemiya's managers, Yayoi Kayahara and Nozomi Kobayakawa, get Yūto and Haruka to take a picture together. That night, they have a ride on the Ferris wheel and confirm their relationship, though not without the hijinks caused by a quite shaky Ferris wheel. Haruka's picture is taken to capture the moment. Yayoi and Nozomi then formally embarks on their real agenda for Haruka: grooming her into an idol.

Haruka agrees to attend the audition for Yayoi and Nozomi. Yūto waits as Haruka gets ready for the audition, and is told by Yayoi not to interfere. While waiting, Yūto once again bumps into the girl he met before at the shrine, who turns out to be the idol Milan Himemiya. Milan decides she wants Yūto as her manager since her own manager is currently in a different prefecture. Yūto and Milan go around together to photo shoots, voice acting and other things. After his work as a manager, Yūto overhears Yayoi and Nozomi while poring over Haruka's photographs. It becomes clear to him that the talent agency actually wants Haruka to become an idol—something Milan had tipped him of earlier.

Yūto has to make a tough decision of whether to stay with Haruka or leave her so she can become an idol. Yūto asks Milan to attend her concert on Valentine's Day. During the concert, Yūto, with some "on-stage prodding" by Milan, decides to leave so as to go to Haruka's audition. Shiina is worried about Yūto and Haruka's relationship. Yūto decides that he wants to stay with Haruka and it is finally revealed to the unaware Haruka how Yayoi had planned to make her into an idol. Yayoi and Nozomi try desperately to stop him, but Haruka's family and maids help to get the upper hand against them. The final blow comes when they are later forced out of their talent agency after Haruka's father buys it and all associated material from them in a hostile takeover. Later at the Nogizaka mansion, as Akiho and Gento watches Yayoi and Nozomi in some mud wrestling contest on TV, Haruka gives a Valentine's present to Yūto.

Yūto is invited to come with the Nogizakas to a ski resort in the mountains. He thinks it is just for them but he quickly finds out the entire class is coming on this trip. While the group enjoys all the hot spring resort has to offer, Shiina sees the trip as an opportunity to express her feelings to Yūto—but in an attempt to hug him, she ends up groping Gento, who was covered in sheets. An enraged Akiho catches them in a compromising position and gets the wrong idea, causing Gento to pass on the group's shrine visitation the next day. The next evening, a blizzard arrives and Haruka goes missing on the top of the mountain. When Yūto, equipped with an insulated polar bear suit, finds her, they both fall down a ridge and become stuck in a cabin. As she is wet and freezing, Haruka takes off her clothes and joins Yūto in his bear suit in just her underwear.