dont be reprized if madara poped up dragon mode and b1tch slaped all haters on face ... anywaysHASHIRAMA's SAGE MODE
Senpou Mokution was used by Hashi to summon shinsuusenju
His markings and and signs are the same as jiraya and narutos when entering sage mode.
his markings look similar to tsunades when she uses her self recovery technique
SENJU CLAN of the FORREST were the Rivals to the Uchia
The only remaining sacred place in the manga to rival the importance of mount myoboku or Ryuchi the Dragons ground cave is shikkotsu forrest (sorry about spelling)
It is ignorant to say that naruto and jiraya would be able to use sage mode and Hashi the god of shinobi couldnt.
Sage arts can only be taught in extraordinary, sacred places by animals who have obtained enlightenment and equilibrium with nature.
The only remaining place like this we are yet to see is shikkotsu forrest, where hashirama senju of the forrest clan, learned mokution and sage mode. It is also relevant to note how their student hiruzens summon is the monkey king enma.
unfortunately the only remaining summon of the legendary sannin is tsunades slug. hopefully the sage mode does not encompass slugs but rather a cooler summon, explaining why tsunade cannot perform this sage mode.
Shikkotsu forrest translates to damp bone forrest. The translation itself says damp. Water element charka mixed with earth chakra is used to create mokution. This sacred place is where hashi learned his unrivaled mokution.
The manga does foreshadow towards the animal/teacher being a slug due to slugs healing powers and hashiramas ability to heal himself. Maybe tsunade wasn't skilled enough to handle this sage mode similar to orochimaru.
In conclusion, Hashirama learned his sage arts and mokution at the shikkotsu Forrest
what i am saying is , anything is posible atm , and for these two ..