u/Anime_Hitler69

I tried to look it up online, and what I found suggested this is an alternation of the two notes on after another until the next part (so the first part got the right hand would alternate d-a-d-a etc.) but when I look at the video (https://youtu.be/VHJzRSICfj4 at around 3:40) it seems like he presses a and d at the same time and alternates his left hand with his right. This becomes more noticeable later in the part.

Just for the record, this is his own official sheet music, so if it is different it is probably on purpose. I also noticed the tempo of the sheet music seems about half that of the video.