As someone who has lived in Korea for 2 years and Japan for 1 year I can say your observation is understandable but would be very insulting to any japanese or korean. It's like saying aren't the Hatfields and McCoys actually related to each other. There's a lot of history between the two thats goes back hundreds of years. And none of it good.
The Korean Kioti company is taking away market share from Kubota and you can believe Kioti took aim on Kubota as their prime target. But can ya prove it, i think not. But ya can deface Kioti a little with a lawsuit. Will they win, nope, but thats not the point. As the years go by you will see different strategies being played out by the 2, I'm waiting on the price war to start.
Koreans and the Japanese copy anything and everything that is sucessfull and if they are sucessful at selling the item then they change it a little and call it their own.
And as for Daewoo, it is one of or the largest company over there. Everywhere you look you see Daewoo. Come to think of it I've never seen a toyota in korea or a hyundai in japan,lol.