It is now confirmed by The Legend of Zelda: Breath of the Wild Director Hidemaro Fujibayashi that the 900 Korok seeds that you took so much time and effort to collect are actually Korok poop.
In an interview with IGN, Fujibayashi thought that it would be fun to make the Korok seed’s backstory one big joke.
“We just kind of thought it would be funny to make that a big joke,” Fujibayashi told IGN, laughing.
“It’s just the backstory, the kind of hidden kind of thing in the game the whole way is that the Korok seeds are actually Korok poop.”
To add on, after collecting all those Korok poop, Hetsu’s reward is a bigger lump of golden poop. Well, I don’t want to judge a race that use their poop to sound their maracas, but at least they increase my inventory space.