Who was the mediator in kōhaku number 53?
CREATE TABLE "table1_1315616_1" (
  "k_haku_num" real,
  "date" text,
  "red_team_host" text,
  "white_team_host" text,
  "mediator" text,
  "winning_team" text
);
SELECT "mediator" FROM "table1_1315616_1" WHERE "k_haku_num"=53;