The background of making the movie (in 2013) is discussed here:
https://en.wikipedia.org/wiki/The_Eternal_Zero
The movie was based on the novel "Eien no Zero" by Naoki Hyakuta.
Toward the end of the article, in a section called "Other Media", they discuss a three part made for TV version of the story which was shown on TV Tokyo in 2015. The TV version used different actors and also included some different sections of the original novel.
Movie Version (with cast list):
https://asianwiki.com/The_Eternal_Zero
TV Version (with cast list) :
https://asianwiki.com/The_Eternal_Zero_(Japanese_Drama)