If a girl jumps from a 30 foot story building and her skirt doesn't fly up, that's dumb. If a girl gets thrown 400 feet into a wall and her boobs are hard as rocks and don't move, that's unrealistic. If a girl has no shirt on, so the fuck what? A girl in a bikini is fanservice, but a guy in a bikini isn't? A closeup on a guy without a shirt on is okay too? Double standards for the lose people. Nothing wrong with "fanservice"
This Highschool of the Dead OVA is fun and entertaining, it gets the job done. If you like the series, this honestly shouldn't make any difference to you because you've already seen how Highschool of the dead gets.