This is a posable action figure from the figma series.

From the Good Smile Company website:

A "Kurogo" is a stagehand that manipulates scenes on stage dressed in black so that he cannot be seen. This figma is designed to support your other figma figures as a stage hand to recreate some bizarre poses! It was decided to be made into a product as one of the proposals made during the Hobby no Tora section of the WonHobby live broadcast.