The sign language in Gangsta.

maihor:

The sign language used in Gangsta. is being supervised by the Tokyo Federation of Deaf. Specifically, the characters are communicating through Japanese Sign Language (JSL).

Thank you (ありがとう): Put your left hand palm-down in front of your chest. In a 90 degree angle, lightly touch the back of your left hand with the edge of your right hand, as if you’re doing a hand-chop. Then lift your right hand back up to your chin level.

Together (一緒): Hold both your index fingers out and then bring both hands together until the fingers meet in the center. It’s a multiple meaning word that can mean other things such as “agreement”.

Here’s an online JSL course in English if you’re interested in learning more!