In this scene we see Tomio Imamura vs. Masao Kagawa. As we can see they are wearing no hand- , mouth- or shin-protection in their kumite. Because it is a non contact kumite.
This circumstance demands absolute body control from both competitors. If only one blow would hit and blood would flow, the attacker would be immediately disqualified. This fight is completely different as we see it today in modern karate with all the different body protectors. Conclusion – the rules determine the fighting style. Think about and remember in self-defense there are no rules, only the moment of truth.