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: Koko Wa Greenwood
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.
Cargo Ship: Until Yuko, his bike may as well have been his girlfriend.
Character Exaggeration: Nagisa, especially, gets this bad. In the manga, she's an unfavoriteRich Bitch who is hellbent on getting Shinobu at her mercy, with a well executed Freudian Excuse. In the OAV, she's still an unfavoriteRich 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.