The article that I linked to has a link here referring to how the original composer, Keigo Oyamada, for the opening ceremony resigned after it was revealed that he did some horrific ****. The video game medley that played during the parade of nations was an impromptu addition, as no one wanted music composed by such a scumbag.

Here's an excerpt:

Soon after the announcement on Thursday, past interviews with Oyamada resurfaced and sparked anger on social media. The interviews were from the January 1994 issue of the Rockin'On Japan magazine, and the March 1995 issue of the Quick Japan magazine. In the interviews, Oyamada confessed to bullying classmates and disabled people in his youth.

According to the Tokyo Sports website, in one of the interviews Oyamada stated he wrapped up someone in a mattress, and also locked a disabled person inside a vaulting horse. The Nikkan Sports website additionally reported that in one of the interviews Oyamada stated the bullying and abuse also included having someone rolled up in string while naked and making them masturbate, and also forcing someone to eat feces. Nikkan Sports added that Oyamada said, "But I didn't do these things firsthand, I just offered up the ideas (laughs)."

Oyamada then issued an apology on Twitter on Friday, stating, "I feel deep regret and responsibility for not being a good friend and for being on the side causing hurt." He admitted in the apology that he bullied his classmates, adding, "It is true that I spoke without remorse about my heartless remarks and actions against classmates and people with disabilities in neighboring schools when I was a student."
Sorry, I guess I was under the impression that this is something that had made the rounds around the internet already and was common knowledge.