What exactly is the condition to hit a tsbumae gaeshi? Why doesn't fuji just always hit this ball - like he did during the fudomine match? I mean seriously if I was fuji and playing against somebody I would just spam this move.
If you have a topspin ball then the opponent actually needs to reverse the spin which takes more energy. Now lets think of a flatball - you have no spin to reverse therefore the spin you add is actually greater. If they had hit a topspin ball then it would take fuji more energy to hit his higumi otoshi.