Question: What is the latest year of a Gratitude type mission with 99 in the entourage?
SQL: SELECT MAX("Year") FROM "2-15718413-1" WHERE "Number in entourage" = '99' AND "Mission type" = 'Gratitude';

Question: Who was the lead envoy of the mission with the Ryūkyūan King Shō Eki?
SQL: SELECT "Lead Envoy" FROM "2-15718413-1" WHERE "Ryūkyūan King" = 'Shō Eki';

Question: Who was the lead envoy of the Congratulation mission in 1718 with the Ryūkyūan King Shō Kei?
SQL: SELECT "Lead Envoy" FROM "2-15718413-1" WHERE "Ryūkyūan King" = 'Shō Kei' AND "Mission type" = 'Congratulation' AND "Year" = 1718.0;

Question: Who was the lead envoy with the Ryūkyūan King Shō Kō?
SQL: SELECT "Lead Envoy" FROM "2-15718413-1" WHERE "Ryūkyūan King" = 'Shō Kō';