San-or-Sensei way of calling in Japan

Japanese culture, for example about an appropriate way of calling Japanese people in Japan, causes some notice and confusion for those who start working in Japan. 

Assuming that you call Ryuho KATAOKA at work, and you are a young researcher, followings are examples to get some varieties and their nuances. 

A) Kataoka-san is more official way of calling compared to the option B, and can be used everywhere. Between professionals in Japan, family name + san is perfect to call each other. 

For example, starting email by writing “Dear Kataoka-san“ is great. 

B) Ryuho-san sounds good to indicate a more friendly relationship compared to the option A. It is good because it sounds like a colleague. This is not very different from "Hi Daniel".

“Hey Ryuho-san, you missed a pizza-magnetosphere meeting yesterday. Guess what happened.“

C) Japanese students sometimes call me Kataoka-sensei, because "Sensei" means teacher, mentor, and/or master. This is not different from the professor way of calling in English, e.g. “Hello professor, you dropped a 24 TB hard disk.“

Only a few good old friends call me just “Ryuho“ in Japan. Finally, if I were a boy, you can call me "Ryuho-kun." There is a professor who call me "Ryuho-kun". He knows me for 25 years since I was a boy (undergraduate).