YMMV / Oniisama e...

  • Ear Worm: Don't expect to watch this series without catching yourself humming the opening theme at least once.
    • Considering that it's an enka-like song with very pretty lyrics, it may double as Crowning Music of Awesome.
    • The ending theme is pretty catchy, too.
  • Hell Is That Noise: The ominous music that plays whenever Fukiko and the Sorority members come into the scene. Double if it's played right after Nanako goes through something bad.
  • Les Yay: A given. Rei has some with Kaoru, then some more with Nanako. She also has it with Fukiko, but...
  • Moral Event Horizon: Some people consider Fukiko's horrifyingly cruel Hannibal Lecture to Rei in the manga to be this. Specially because Rei ends up commiting suicide few afterwards.
  • Narm: A non-drama example: Aya Misaki's horrible puffy hair. May have been in vogue in The '70s when the series was written, but now...
    • As well as the ridiculously exaggerated faces she makes after Mariko slashes her with her boxcutter.
    • In the third episode, when Aya and her Girl Posse bully Nanako in English class and almost everyone joins in until Kaoru intervenes, the absolute incompetence of the teacher makes the whole drama bomb almost comical. One can understand being put off by a bunch of schoolgirls whining in the middle of a lecture, but letting a kid half your age put order? What kind of teacher is this?!
    • Mariko's hot bath of angst is rather sad... until she starts floating down on her belly, with her bare ass sticking up. How the HELL didn't the people in charge of that scene notice how stupid it looked?!
  • Values Dissonance: Lots of people are weirded out when the Seiran students make such a huge deal of Nanako's mother being re-married to Professor Misonou (aka Takehiko's estranged father), but it makes more sense when we remember that the Japanese society's stance on divorce, adoption, and Sins of Our Fathers are pretty different to the ones in the West. And there's also the fact that this particular manga was written in The '70s...
  • Wangst: Fukiko, who cannot get over the fact that Takehiko didn't come to her violin recital when she was 12... which happened six years ago.
    • Lampshaded by Rei in episode 25, when recalling her and Fukiko's first meeting. Young Fukiko was in tears over being shabbily treated at a friend's party (read: she didn't like the seat she was given) and young Rei was all "... is that ALL?!"
  • What Measure Is a Non-Badass?: If you watch this series on YouTube, PLEASE be careful while reading the comments. Lots of people there love to bash Nanako and call her "weak" or "stupid" for not kicking off her bullies.
  • The Woobie: A lot of them:
    • Nanako and Rei. Poor little Nanako, so sweet and so kicked around by life itself. And poor Rei, so utterly broken ever since she was a little girl. Also, episode 15 brings a character we didn't know about, then breaks her, and makes her this. Poor, poor Junko.
    • Jerk Ass Woobie: Mariko and anime!Aya. Mariko is utterly clingy and possessive of Nanako, to homicidal and self-destructive degrees, and can be a bitch to Tomoko in the beginning. She's also among the few willing to protect Nanako from bullies and help her in the Sorority, and is genuinely fucked up from her parents's MESSY divorce, which drives her to almost kill herself; not to mention— gosh, when she shows a sweeter side, you almost wanna say "Mariko why so moe"? On the other hand, Aya Misaki's JAW phase comes very late in the TV series: for all of her horrifying, bitchiness, we learn that she has enormous inner self-hate, and she almost kills herself after the Taking the Heat incident.
    • Iron Woobie / Stoic Woobie: Kaoru and Takehiko. Kaoru does what she can to deal with her woobielicious best friend Rei being totally broken, with trying to support Nanako so she won't be fully broken as well, and her own ailing health; meanwhile, her boyfriend/eventual husband Takehiko almost always smiles kindly and tries to be a good friend, despite how he can't tell Nanako that he's her stepbrother aside of her pen-pal, which puts quite the spin in their interactions, as well as his own relationship with Kaoru. (And we're not counting the manga, in which Kaoru actually dies a while after they reconcile...)