@pbrgh
You misunderstoob me a little. One thing if someone who you know asking YOU. Like your classmate come to you when you walking with friend and saying "Hi man", introducing himself to your friend, you introduce your friend to him etc. Its normal polite conversation. Whatever rumors will be after - doesnt matter.
And the other thing when you are walking with your friend and some random classmate that you now only "he is in my school" suddenly come to you and starting to harass your friend like "Omg lol who are you whatcha doing" - THIS IS RUDE. FOR THIS - i would ask this person to get lost myself not even waiting my friend to answer this nonsence.
Same here, in this (and lot of others) mangas - its like their really bunch of chickens - KO KO KO. I get what author tried to do there, but this is just looks idiotic, like all this girls were raised in a barn.
Try to picture not some situation like you describe, try to picture yourself in this manga situation. What is this school and this kids? They like gipsy's on the market wanting to rob you.
Anyway, this is just my opinion - i see this plot like "omg this guy is so shy but popular that all the girls want to eat his dick even they dont know him - so they gonna murder any new girl seeing him" so often that it makes me sick. Or - another one version - girl in the school make a pact not to date this guy so there was no need to kill each other over him but then new girl coming and they harrasing her - another one cliche. Maybe - maybe - this crap is really normal for japaneese schools (all asians crazy about their idols etc), but for european it looks like some Middle Ages and this girls like Inquizition.