Well, it turns out that the West is primarily the reason why Japan has a panty obsession. It is also fairly new. It started in the Meiji era (1868-1912) when western clothing started becoming popular with the wealthy. Common people still wore kimono and koshimaki, a traditional waist wrapped undergarment.
During World War II, women were encouraged to wear loose pants with ankle drawstrings called monpe. Because they no longer could wear koshimaki, women started wearing western style undergarments called drawers. After the war, Japan suffered from extreme poverty and the only women who could afford to wear the more expensive Western underclothes were the high-class prostitutes that serviced American and Ally soldiers. Western style underclothes quickly become associated with sexual promiscuity.
After the economy began to recover, women had more spending money but there was still a shortage on fabrics. Ladies began spending more money on the newly imported panty and its more expensive fabrics and styles. The government also promoted the panty over the “more revealing” tradition undergarments worn in the past. Because women were not used to wearing Western style underclothes in combination with Western style skirts, they were not used to sitting with knees touching. They were not used to moving in ways that kept underclothing hidden. Shame in displaying these undergarments developed; this shame was originally foreign to wearing the koshimaki.
These factors all come into play for the Japanese panty fetish. First, panties were long associated with the risque. Not only do they cover up desirable bits, but they also have a strong association with high-class prostitution. Second, panties tend to reflect a lady’s personal tastes in fabric, lace, and design. They also have connotations of wealth since originally only the wealthy could afford such luxuries. Finally, the up-skirt shot originated from when women were adapting to the less constrictive Western styles and developing feelings of shame with underwear exposure. These associations merged into the panty fetish and fan service we see in Japanese culture and anime today.
The introduction of female underwear and the emergence of physical shame in Japan. JapanReference Retrieved February 13, 2013 from http://www.jref.com/japan/society/japanese_underwear.shtml
Meiji Era. JapanReference. Retrieved February 13, 2013 from http://www.jref.com/japan/history/meiji_era.shtml
Images from Rosario+Vampire Season 2 Published by Shueisha.