Mizuno is shown to have a more "childish" concept of interpersonal relationships. Social cues and nuances fly right over her head, and romantic cues straight up bounce off it like ricocheting bullets.
When it's suggested that she should behave like a "chased woman", she thinks of it in a literal sense, being physically chased down through the school over an erased. When she's urged to make amends with her exiled school friend, she hears the term "being looked down upon" and then goes on a tangent about how she's taller than her friend. She answers her friends' requests without even knowing why she's doing it in the first place.
When beating around the bush in a date with Tanaka, she gets distracted by something on almost every page, and then decides to discuss the whole confession thing at a kids' playground. She seems to be clueless on how to interact with people to a rather extreme level, it's really no wonder that she chose not to get into a relationship. She outright says she doesn't even know what a relationship is about.
I wonder if her name being Mizuno (water) is intentional - she just goes with the flow without thinking about anything.
