These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
YMMV: Nana to Kaoru
Ensemble Darkhorse - Mitsuko Tachibana, the porn store manager. Such joy. Such perversion. And soinformative too. In the Time Skip pseudo-sequel series Nana to Kaoru: Black Label, it turns out that she's the personal slave of Shuutarou Sarashina, Kaoru's favorite BDSM author... who then invites Nana to a countryside retreat. Sarashina invites Kaoru to the retreat around the same time.
Fetish: If you didn't have a BDSM fetish before reading this manga, you will by the end of it.
That isn't even the half of it. Read it too much and it all starts to seem positively wholesome.
Plenty — plenty — of BDSM practitioners would reply to that with: "That's because it is." The only major research failure with the series is the lack of safewords, other than that it's pretty much been a textbook lesson in a wholesome BDSM relationship.
he captain of Tachi's track team, Yuuki Haruka, who not only is the only one who cheers her on during her race with Nana, but also looks bashful and hides when Tachi looks into the crowd after she wipes out with Nana in the middle of the race.
Moe: When Kaoru finally - awkwardly, painfully - tells someone that he loves Nana, admitting it to himself in the process. "The pitiful kind of moe", indeed.
Narm Charm: Amazume manages to make an anal suppository heartwarming.
Ugly Cute: Kaoru, moreso when his love for Nana is concerned.
Values Dissonance: The lack of Safe Words may raise some eyebrows amongst American readers - they're far less common in the European and Japanese S&M scenes, where considerably greater responsibility is placed on the dom for the safety and enjoyability of a session.
In some ways this can be seen as a sign of an even deeper divide. In America, acknowledging sexual desires is the norm, where in Japan it's looked down upon to be too open about your desires. So, where many Western kinksters could read this book wondering "why doesn't Nana just SAY she wants this..." in Japan it's considered quite normal that she isn't able to.
Viewer Gender Confusion - Tachi never mentions her actual gender, thinking that it was obvious... Even though, in her jogging suit, she's masculine enough to fool everyone who sees her.
It's pretty evident that everyone is judged by Kaoru to be unworthy of Nana, including himself. To hear him tell it... he is scum of the earth and utterly unworthy to even be around Nana, despite being obviously in love with her dearly.
It's easy to feel bad for Nana as well. As readers, we see Kaoru's inner thoughts and more sympathetic sides, but to her he must seem like a horrible person with a Hair-Trigger Temper.