There isn't much in world art history that is considered more an outpouring of the soul than poetry, and with the Japanese Zen aesthetic and the intensity of its poetry, it's very easy to see their poetry that way. However, poetry was a competitive activity from early times. The first poetry contests, called uta awase, are recorded in the early 10th Century. There were teams, points and prizes. In the early 13th Century, there was one contests with 1,500 rounds, the winners collected into a big anthology. By the 17th Century there were speed poetry contests, which apparently often comprised "exercises in demolition", which makes that sound rather like battle raps. By the 18th Century, there was an established points system for rating haiku.
An extra personal note that I want to include here is that I am finding it very hard to research the immense history of contests in Japanese arts, so I would be very grateful to anyone who can point me at any useful books or websites.