Pretty old video. Japan-held matches are known to staged (and confessed by fighters on making offers to throw fights) for publicity and other reasons. Surprise sucker punch or not, he threw that punch with mostly his bicep/forearm. We both know that's not how you throw a punch. It doesn't look like he was aiming to hurt. Also, carefully examine the emotion he put into it.
Is that Genki Sudo reffing?
“If you worry about what might be, and wonder what might have been, you will ignore what is.” -anonymous