Sō clan
Korean diplomatic efforts produced an agreement in 1443, also called the "Kakitsu treaty" after the Japanese era name ("nengō") which identify the years 1441 through 1444. The agreement regularized an initial plan for mitigating the damage caused by pirates. The bilateral agreement assigned the responsibility for monitoring ships from Japan en route to Korea. The Sō clan of Tsushima han (Tsushima Island) were given the right to license ships sailing west beyond Tsushima; and this also encompassed the opportunity to profit from whatever fees the Sō might charge.