I couldn't manage to form the skull robot's hands of both sides into what I was satisfied with, so I smeared away and erased them.
Then, the composition got some feel of openness.
Taking this occasion, add purple with low color saturation that is a complementary color of yellow to the background and further express the image that gas came around.
Draw Sechs' hair on the top layer.

It's been getting better for the whole, but still it is not completion.
I'm going to further raise the quality from this.