Maybe this could have been the so called "Hitogata".

DISCLAIMER: THE FOLLOWING REPORT IS OF A VIDEO THAT WHILE IN THE SAME TIMEFRAME AS HITOGATA, IS NOT A RECREATION OF THE AD AS STATED IN THE VIDEO'S DESCRIPTION. ALSO, THE VIDEO DESCRIBED IS NOT MINE! THE RIGHTS BELONG TO THE RESPECTIVE CREATOR(S).

I like to watch this channel called cm1980810 (Yes, that's the actual name.) which uploads recreations of lost or old public service announcements. The most recent upload which is titled 【迷宮入りCM】児童虐待防止（AC公共広告機構？）(Translated as [Commercial with labyrinth] Prevention of child abuse (AC Public Advertisement Organization?), features two white figures on a black background. The white figures then start doing jumping jacks until a larger red figure appears on screen and repeatedly hits one of the white figures. We then see a blue figure run on screen who tries to stop the red figure from hitting the one white figure but fails and the white figure that was being hit collapses causing the blue figure to cry out in terror (It could also be the other white figure however it is most likely the blue figure.) as the AC Japan logo appears on screen with a narrator saying the company's slogan. My guess is the fact that people saw the ad and incorrectly memorized parts of the ad which caused the whole Hitogata story to develop. The ad was also aired in the 2000's to the 2010's which is when reports of Hitogata showed up so that's what makes me think that this could be the ad people saw. Here is the link to the video: https://www.youtube.com/watch?v=5TEFTCfqY0w 0