Kaoru is a 17 year-old virgin who has an undeniable affinity for S&M. He has always dreamt about engaging in such practices with his childhood friend, Nana, who is often looked upon with perfection at their high school. Their friendship has somewhat deteriorated through the years, due to them hanging out with other people, and also because Kaoru refuses to take his education as seriously.
One day, Kaoru's mother gives some of his S&M collection to Nana for safekeeping. This leads to her investigating these belongings, and eventually giving the most interesting part of his collection - a one-piece, leather dress - something of a trial-run. After trying it on, she accidentally locks herself into the dress, and is pained to discover that the key wasn't with the outfit. She reluctantly contacts Kaoru, who after living a brief moment of his fantasies, who proceeds to free her of the one-piece. However, Nana realizes that she may enjoy Kaoru's hobby more than she previously thought, and the two subsequently start to engage in her so-called "breathers."
After an unfortunate end to one of their breathers, Nana approaches a beat-up Kaoru.
Accepting Nana's request for a breather, Kaoru ties her up and takes pictures of her for the sake of the event.
During their breather, Kaoru pretends to go follow his own desires in order to breach and compromise Nana's sense of security around him. This escalates into massaging her feet with a gooey lubricant.
Nana summons Kaoru for a breather by knocking on her wall, but plays coy when he arrives.
Nana continues to pretend that she never knocked on her wall, expecting Kaoru to make the first move. However, at the same time, Tachi Ryouko- a friend of Kaoru's, and rival of Nana's - shows up to visit Kaoru.
Tachi discovers Kaoru's plan to tie Nana up, leading Nana to coerce her into joining their next breather in order for her to understand its sensual, and mostly harmless, merits.
Following her experience in the breather, Tachi takes a relaxing bath prepared by Kaoru.
Taking part in another 'breather,' Nana walks out onto her balcony wearing a rather suggestive and revealing outfit.
Nana prepares to tutor Kaoru.
After trying to apologize to Kaoru for the wrong reasons (her own ease of mind, rather than because she genuinely felt apologetic), Nana agrees to be spanked as a form of punishment that he decides would be fitting.
Nana undergoes her punishment 'breather.'
Left vulnerable from her spanking, Nana awaits Kaoru's return with cooling skin ointment.
Tachi finds her way into Kaoru's room once again.
Following her unwelcome arrival, Tachi successfully forces Kaoru to take a 'breather' with her, resulting in her being tied up as practice for Nana.
Tachi's 'breather' comes to a miserable end, with Kaoru suffering an arm injury because of her decision to leave the apartment while still tied by his rope. Still, she decides to sleep over next-door with Nana, because of her exhaustion.
Nana overhears Kaoru talking about anal with his friends at school, and makes the horrifying decision to look up said practice on the internet.
Nana gets sick and is subsequently recommended a suppository to ease her sickness.
Nana prepares for another 'breather,' although this time Kaoru states it would be much more intense than any of those that came previously. This is in part because of his plan to reveal his true feelings for Nana, although not to her face.
Nana undergoes the breather, finding herself immobilized and blindfolded, effectively reduced to "a piece of meat."
Nana and Kaoru continue their increasingly emotional breather.
With the interruption of several of Nana's classmates, Kaoru ends the 'breather' and unties Nana, but not before revealing her legs have gone numb from being bound so long.
Tachi decides to milk her friendship with Kaoru for all its worth, requesting that he attends the sports meet where both she and Nana will be competing. They go behind Kaoru and decide without him that whoever wins their competition will undergo a private 'breather' with Kaoru.
Nana decides to give up her right to the 'breather,' allowing Tachi to take it while she dogsits for one of her classmates.
Nana is caught roaming about Kaoru's apartment in a well-laid trap by both Kaoru and Tachi, with the goal to draft Nana into their 'breather' as punishment for snooping.
Nana and Tachi equip their dog-like equipment at the request of Kaoru for their shared 'breather.'
After a minor hiccup during their semi-successful 'breather,' Nana returns to continue.
As the stress in Nana's life accumulates because of her parents' estranged relationship, greatly impacting her performance in school and with her friends, she contemplates summoning Kaoru for another 'breather.'
Kaoru serves as a distraction to Nana's troubles, initiating a heavy 'breather' within minutes of his arrival.
Kaoru and Nana continue the heavy 'breather.'