Yumiko has the most boring personality (it never grew on me), the dullest backstory, and yeah, her route's storyline is really similar to Makina's, only not as good. There are certain people who fall for her deredere mode, but she only ended up getting on my nerves. All of the girls are too dependent and submissive, but she was the worst. If you read her route first, it's probably not as bad because you haven't seen Makina's yet.