>>8694510
Because Shiraki is the best girl in the series. Proof: She gets raped the most.

Also, no only was her design used in later hentais (discipline's Leona for example), but caused many young coomer to develop a fetish for that particular hairstyle.

Sidenote, a few years ago I got a new coworker with that exact look. Blonde, Shiraki-hairstyle, big boobs. Made going to work simoulteanously better and also worse, if you know what I mean.