Hello!
I am an avid 16 year old pianist, at an intermediate skill level (I consider it to be intermediate, at least). I am looking for advice on the best way to learn an extremely difficult song. The hardest songs I currently know how to play are Taioo's version of the Skyrim theme, found on YouTube, of which the left handed appregios took a very long time to learn (although, I didn't actively try to learn it, as in practice everyday). The other song is called Kawaranai mono, from the anime movie The Girl Who Leapt Through Time, which took me 3 months of practicing every weekday for 40 minutes straight, much to the annoyance of others.

The song I have been yearning to learn is called This Game from the anime No Game No Life. If you look it up on YouTube, I want to learn Animenz's version, of which the sheet music can be found here:
https://sheethost.com/sheet/8sUORu . I understand that this piece has a drastic (understatement) difference in skill between the skill I have now, and the skill needed. This will, optimistically, take 1 year of solid practice for me to learn.
I would like to know if anyone has any advice on the best approach to learning this song could be, or any difficult songs for the future. I already know to learn both hands TOGETHER from the start, as learning separately means you have to essentially relearn the song, but with both hands together.
Thank you for reading this entire post, and for anyone who takes the time to comment!
Sincerely,
Dante Fragapane