Hello guys,
As I run into more complex songs and, being initially a guitar player, I naturally want to use my middle finger or pinky finger instead of moving my hand (lazy !). But I can’t find any video where shamisen player use them so I am questionning : are we allowed to use them or shall we only use index and ring finger ?
Thanks,
Florian
You can use all your fingers! Even the sixth finger😂 like in @Kyle_Abbott 's book😸.
The placement of index and ring finger on the fretboard is ideal for pressing most notes, but even middle finger is also used quite often. There are some people who use middle finger instead of ring finger. So finally it’s upto the individual to use any or all his fingers while playing shamisen 
Watch Kanami San playing at 4:00 minute mark in the below video.
Nice, thanks 
I haven’t received the book yet, no spoil ! 
Traditionally, we use the first (hitosashiyubi), second (nakayubi), and third fingers (kusuriyubi). The fourth finger (koyubi) is not used.
However, you will find some modern players that utilize the fourth finger, particularly when trying to play outside of traditional genres - Reigen Fujii specifically has mentioned it in the context of jazz.
Personally, I find it very awkward - but I was traditionally trained :p.