@Joel Wish fulfillment fantasy + writer not building motivations enough to be convincing. It works if the characters already have history, or if the person who gets attracted has an obsessive/troublesome personality that becomes a plot point and explains the behavior. Characters who are supposed to be mostly normal pushing this much right after meeting MC is a little over the top.
I prefer when behaviors fit the setting. Stories like Golden Time or "Ookami Shounen wa Kyou mo Uso o Kasaneru" handle characters developing feelings well...and the latter pulls it off in spite of a ridiculous premise.