Sensei (先生) is a Japanese word, indicating a form of respect, and can have several meanings
- It can be used to address one's teacher.
- Or generally speaking someone strong enough to be a teacher.
- It can also refer to an older player.
The -sensei ending is one example of a Japanese name suffix.
Sidenote: in Hikaru no Go, an older player comes into the club to find 11-year old Akira Toya, a kid aspiring to become a professional Go player. The man asks if Akira Sensei is present. Mr. Kitajima, a player at a Go salon, tells Harumi Ichikawa to call Akira "sensei". Akira later states that he would feel awkward if Ms. Ichikawa called him "sensei".
One can imagine that Yoda Norimoto will call Sakata "Sensei", although Yoda is probably stronger at the moment.