I am searching for the name of a manga.
What I can remember:
There was a younger guy getting trained by someone older.
And to get more training done, they split their 24 hour day into 12 hour days. So MC eats train sleeps in a 12 hour cycle instead of 24 hours.

I think he also bulks, (gets fat) and then they are training again.

That should be relative early chapters. I read that years ago…

I know this isn’t much info, but I am trying my luck 🙂