How do you say hello friend in Japanese?

If you are close to your friend, then you could just say their name and add -Chan on the end. This shows that you are close to that person. You shouldn't use it if you don't know them too well, as it is quite casual and would be disrespectful.

'Hello' depends on what time of the day it is. Common ways to say 'hello' are:

Morning = Ohayou ?-Chan

Afternoon = Konnichiwa ?-Chan

Evening = Konbanwa ?-Chan

For example, it would be "Konnichiwa(Friend's Name)-Chan".

You may also say こんにちは、友よ (konnichiwa, tomo yo), which literally means "hello, friend".