There are two Japanese major leagues, the Pacific League and the Central League. Together they are known as "Nippon Professional Baseball" (or "NPB").
Unless the player is released or signed by an MLB club after being posted, all NPB players remain under club control (the player is "reserved") for nine seasons. After the 9th season, the player becomes an unrestricted free-gent.
1. An NPB player who is not under the control of an NPB club can sign with any MLB club.
2. With the consent of the NPB club, an NPB player who is under club control can be "posted" (made available to be signed by an MLB club) anytime during a three-month period extending from November 1st to February 1st.
3. The NPB club decides in advance on the amount of the release fee it will be paid if the player signs with an MLB club (it can be any amount up to $20M), and all MLB clubs are notified of the posting by the MLB Commissioner.
4. Any MLB club willing to pay the release fee can negotiate with the NPB player during a 30-day period starting on the day after the player is posted.
5. If an MLB club signs a posted NPB player, the NPB club receives the designated release fee from that MLB club. The release fee can be paid in installments over an 18-month period, with the MLB club required to pay 50% of the release fee within 14 days of the submission of the posted player's contract, 17% of the release fee within six months of the submission of the posted player's contract, 17% of the release fee within 12 months of the submission of the posted player's contract, and 16% of the release fee within 18 months of the submission of the posted player's contract. (The release fee is not considered when calculating the MLB club's payroll).
6. If a posted NPB player does not sign with an MLB club within 30 days after being posted, the NPB club does not receive the release fee, and the player cannot be posted again until the next November 1st (unless he becomes an unrestricted free-agent in the meantime).