Honestly, Shizune was the second worst girl.
Not as a character, but as a story.
The problem with Shizune's path is that there was never any actual love, any passion.
Shizune was a typical high school fling, and that is shown especially in the end, where nobody is sad that they part ways. I don't think they even said "I love you" to each other, but I might be wrong.
The sex was good, but just that. Shizune was never Hisao's girlfriend. She was his fuck-buddy.
