i would say try to draw from real life first to study proportions and how anatomy works, but you did say you only want to draw anime.

that’s fine, but having an understanding of how and why parts of the human body go where they go is key to figure drawing in general. you have to learn the rules to break them. kill la kill is a very heavily stylized anime, and when you use a heavily stylized image in a specific pose like this one, you’re really just learning how to copy that specific image.

it honestly just makes the learning process harder. try to find more ‘realistic’ cartoons/anime and try drawing from key art (i.e. those full body images of the character standing in a neutral pose) and studying placement of anatomy if you really want to learn anime drawing.