Nana Chigusa, Student of Class A, part of the track team and Student Council VP, is a very popular and beautiful girl. With so much riding on her, a teacher suggests she find a way to take a breather. When she is given Kaoru&#039;s toys to hold on to as a punishment by Kaoru&#039;s mother, she inadvertently locks herself into the leather outfit therein, starting the story...

Kaoru is a 17-year-old virgin who has an S&amp;M fetish. He has always dreamt about an SM relationship with his childhood friend Nana, who is looked upon as perfect and is always the target of boys' eyes. Their relationship has somewhat deteriorated through the years, due to them hanging out with different people and because Kaoru is not taking his education too seriously. 
One day though, Kaoru's mother gives some of his S&amp;M toys to Nana for safekeeping - Nana finds the leather one-piece that Kaoru bought and tries it on but accidentally locks herself in it and doesn't have the key! 
Kaoru frees her of the one-piece, but then Nana realizes she may like Kaoru's hobby more than she thought and subsequently the two of them start engaging in so-called "breathers". These breathers are intended to relieve Nana of stress, stress originating from her attempts at keeping her grades and her name perfect.

__Height:__ 158 cm
__Hobbies:__  karaoke, onsen trips
__Skills & Abilities:__ calligraphy, copying sutras, flute

Kaoru is in love with his childhood friend turned idol, Nana. Over the years, their relationship has become strained with the differences in their lifestyles, but Kaoru still fantasizes about Nana helping him realize his ultimate fantasy... a BDSM relationship with her! One day, Kaoru's mother finds his toys and gives them to the ever responsible Nana to rid her son of his fetish, but Nana finds a leather piece and accidentally locks herself inside! This moment awakens something inside of Nana, whose stressful life could use some fun and could be the start of Kaoru's ultimate fantasy...
 
(Source: Denpa)

During their final summer vacation, Nana and Kaoru’s plans coincide when both find themselves staying at the same mansion in the countryside, with Nana being tutored by adult goods shop owner, Tachibana, and Kaoru by his favorite BDSM writer, Sarashina Shutaro. Wanting to use the couple as inspiration for his next book, the two witness Shutaro's mastery of BDSM with Tachibana. So when Nana witnesses the rawness and intensity of true BDSM, will she look away or will something new unlock in her?
 
(Source: FAKKU!)

The story takes place in the third year of high school, after the ending of the manga, but before Black Label 
 
Note: This series is also sold in compilation volumes under the title Nana to Kaoru Last Year, but the original serialization in the Harem magazine still retains the title Nana to Kaoru: Koukousei no SM gokko, so that will remain the main title.