Download Anima2D Free Unity. 

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Anima2D is a 2D Skeletal Animation plugin for use with Unity 5.x.

Anima2D helps you improve your 2D animation workflow “the Unity way” by including the following features:
– 2D Bones
– Sprite to mesh conversion
– SpriteMesh Editor
– Automatic weights
– Weight Editor
– Inverse Kinematics
– Save / Load Poses
– Atlas compatible
– Bake Animation to Bones
– Onion Skin
– Create Avatar Masks
– C# Source code included