Here Is Greenwood/YMMV


 * Adaptation Distillation: The Dorama. Really, the only thing actually wrong with it is that it's too short, which meant a lot of stories had to be cut or truncated. The writers packed at least half of the manga into those 13 episodes.
 * Character Exaggeration: Nagisa, especially, gets this bad. In the manga, she's an unfavorite Rich Bitch who is hellbent on getting Shinobu at her mercy, with a well executed Freudian Excuse. In the OAV, she's still an unfavorite Rich Bitch who is hellbent on getting Shinobu at her mercy, but her Freudian Excuse is mangled and not really much an excuse at all (in the manga, she explains that her family treats her as next to worthless for being female, and below Shinobu in rank despite being older, but no such preface to the flashbacks is given in the OAV). In addition, she's obviously ashamed of her less than savory predilections in the manga, but has no such scruples and is shown happily molesting Reina in the OAV.
 * Misaimed Fandom: Despite Kazuya being the main character and all stories save two being centered around him and told from his point of view, and despite Nasu's Author Avatar poking fun at the fans for it, most of the fandom is centered around slashing Mitsuru and Shinobu.