I am afraid you took this out of context the enviroment does not have to be
belivabe
any anime, manga, fanatasy, ofr sci-fi story whould have to make allowances
for how
things work in there universe. What has to be plausable is peoples
reactions. If you 
do something in a story that hurts someone. Then that person is not going
to just
pertend nothing has happened unless it suits there purpose. What I am
saying is
that when you write a story show people acting in plausable ways for ther
character.
Don't Just pretend nothing has changed when your character makes a decision
or does
something. Nobody lives in a vacume people will react to your actions. What
I am trying
to say is in stories such as "College Years" and others you have characters
acting
so far out in left feild it is unbelivable and takes away from a good
story. I really
dont care who gets who in what fic. What I look for is fics that explane
why characters
do what the do. And show the others around them reacting in belivable
fasions. In "College
Years" you have Ranma, post manga after six years of being engaged to Akane
decide to marry
Uykou. Akane is a little upset by this, but has no problem with Uykou and
Ranma later
decideing to attend her college, and Uykou even becomes Akanes roommate.
Now tell me
that you can see this with these people. There are a lot of fics like this
it cuts across
series What I am saying is if you are going to do something explane how the
situation
came about and show relistic consequences. 
-Peace