Does any one knows the anime where the main character has a green little friend from another dimension? He and his friend fuse by joining hands.
It's like his buddy and he join bodies and then he has green armor on the main character.
There is one more step I remember his green little friend is small size on Earth but when they travel in another world he changes size to a large one.
They fuse like Goku and Vegeta but in this case his friend becomes an armor on him and gives him lots of power.