Ryokugyu explained himself in the term mother nature, but overall It's not new. He Is made of wood, but his power are broader.
Aokiji Is the same: his too Is not, in fact, the ice fruit: It's the cold fruit. He Is made of ice like Ryo Is made of wood, but in fact his fruit embodies a much general concept (cold) just like Ryo Is nature.
Oda takes a bit of both form eastern and western "idea" of elements, which Is different, and then adds what he wants basically.
Air probably got diveded in 3: Wind for Dragon, Smoke for Smoker and the more general Gas for CC; Akainu is a mixture of Earth and fire and so on.
Aokiji Is the same: his too Is not, in fact, the ice fruit: It's the cold fruit. He Is made of ice like Ryo Is made of wood, but in fact his fruit embodies a much general concept (cold) just like Ryo Is nature.
Oda takes a bit of both form eastern and western "idea" of elements, which Is different, and then adds what he wants basically.
Air probably got diveded in 3: Wind for Dragon, Smoke for Smoker and the more general Gas for CC; Akainu is a mixture of Earth and fire and so on.
