The Forest
.
.
Don't go into the forest.
Those five words were repeated often enough throughout the world, for the citizens of Hi no Kuni it was altered just a bit.
Don't go into Hashirama Forest.
Because while the forests, at large, were safe for those whom called Hi no Kuni home, Hashirama Forest was something else entirely.
It was made up of trees so strong it was said that the most powerful woodsman couldn't even make a scratch in it's wood after a full day of chopping, so large that they towered over every other breed, so thick that if one could carve out a house into its trunk that it would surely be comfortable to house a noble, so rare they grew nowhere else and, if one were to ask one of the Twelve Guardians, so powerful that one couldn't sense individual chakras in the forest just one giant cluster.
The forest was named after Senju Hashirama, the man who grew them- who created them, who some whispered about being a kami donning a mortal body- on land that his brother, Senju Tobirama, had chosen and then declared it home to the shinobi of Konohagakure with his partner, Uchiha Madara.
(Madara was also a presumed mortal-bound kami as he was known to control bijuu with merely a look.
Most, however, viewed Senju Hashirama and Uchiha Madara and all those that followed as monsters.)
Don't go into Hashirama Forest, children are told, repeatedly and fearfully. It is the home monsters; nothing returns from there that hasn't been turned into a monster also.