It has something to do with Japan’s Hinamatsuri (Doll Festival) which is celebrated on March 3 every year.
The festival is also known as Momo no Sekku (seasonal festival of peaches) that ushers in Spring - a time when houses are decorated with plum flowers and emperor and empress hina dolls are placed in places of honor in the home.
Peach Coca-Cola is, like you would expect, a peach flavor infused version of Coke... which if it's anything like the more currently available Cherry Coke or Vanilla Coke, is something that tastes awesome the first time you drink it, and then it's cloying sweetness kicks in to make the second drink less appetizing.
Then again, some people like the overly sweet stuff.
Peach Coca-Cola is available in Japan in a 500-milliliter (16.9-ounce) bottle retailing for ¥140 (US$1.27), and the 280-ml bottle at vending machines available for ¥115 (US $1.05).
Try it... I'm sure you'll like it.
At various restaurants where you are allowed to fill your own cup, I have a Coke Zero filled 3/4s and the remainder with Strawberry Frutopia - so I know the allure of the fruit and cola mixture, but even though I have a sweet tooth, it's not something one can have often or in large quantities.