Japan once again stunned the World Cup in Qatar with another giant-killing effort Thursday that kept the Samurai Blue on course for their first quarterfinals and sparked jubilant celebrations among players and fans. Staring at a potential exit, Hajime Moriyasu’s side evoked their earlier victory over Germany as they came back to beat Spain 2-1 and top Group E on a night likely to be remembered as one of the most enthralling in the tournament’s long history. “I’m speechless. This is why you can’t quit the national team. (It’s the) best feeling ever,” said 34-year-old captain Maya Yoshida, who g…