The art style has changed so much because the artist doesn't have much experience, and by drawing as often as in this case, their progress is faster and more drastic than that of a veteran artist. But the change of style is bound to happen 95% of the stories.
Hahaha, I've read like 2,000 stories and only in a few is the change in the art style drastically noticeable, like in this story, which is super notable, but well, I think the minor problem is the design, the big problem is the story, it's crap ╮(￣▽￣)╭
The changes are more noticeable if you check the first and last chapter of any story, especially manwhas. It's fun to see the difference. Japanese artists have a more consistent style through their works for some reason.
The story is bad and now they also changed the artstyle, they don't look alike at all anymore.... this just keeps getting worse. (⊙…⊙ )