Kon’nichiwa (こんにちは) is a very well-known Japanese greeting. Maybe it is the first word non-Japanese people learn and say. Therefore it is one of the most frequently used words in Japan. But if you say kon’nichiwa to your Jpn friends, they feel awkward.

Why is that? Because kon’nichiwa is supposed to use to strangers. Have you seen an character in Jpn anime or manga say kon’nichiwa to friends? I’m sure you hardly ever see it.
 
Kon’nichiwa is like this.
greetings
 
Kon’nichiwa is a Japanese greeting in daytime. In English, we do not say “Good afternoon” or “Good evening” to friends, do we?
 
The same goes for Kon’nichiwa.
 
Rule:
Do not use kon’nichiwa to someone you know well.

 
Kon’nichiwa is NOT used to…
 
・family members
・friends
・colleagues