It’s basically practice work.I did it a few days ago.
I want to say some technical things.
first of all,The pen sketch needs to be done a little more carefully. Because if it gets stained, it can't be erased anymore.So it has to be done for a while.To facilitate this you can draw a pencil and then sketch a pen. I have used two types of pen black and white pen on boxboard paper.
The use of lines is very important here.
if you enjoy my work. you can find it on others sites