No payments are made when the trade starts. There is a zero-coupon form, which settles once at maturity, and a form that settles every year during the term. In a zero-coupon swap, one party pays the notional amount times the rise in the price index over the whole period, and the other pays the notional amount times the fixed rate compounded over the number of years in the term. In practice, only the difference between the two amounts is paid.
Consider a hypothetical example of a zero-coupon swap with a notional amount of 10 billion yen, a term of 5 years, and a fixed rate of 2% a year. The fixed leg is about 1,040.81 million yen. If the price index rises 15% over the 5 years, the inflation leg is 1.5 billion yen, and the party paying the fixed rate receives the difference of about 459.19 million yen. If the index rises only 5%, the inflation leg is 500 million yen, and the party receiving the fixed rate receives the difference of about 540.81 million yen.