Who was the lead envoy of the mission with the Ryūkyūan King shō eki?
CREATE TABLE "ry_ky_an_missions_to_edo" (
  "year" real,
  "mission_type" text,
  "shogun" text,
  "ry_ky_an_king" text,
  "lead_envoy" text,
  "number_in_entourage" text
);
SELECT "lead_envoy" FROM "ry_ky_an_missions_to_edo" WHERE "ry_ky_an_king"='shō eki';