So, who did Mr. Miyagi beat up and why did he do so ... that he not only competed in the Sekai Takai but also supposedly killed someone. This not only made him investigate further but also ...

Miyagi must have made mistakes and, if he did kill his Sekai Taikai opponent, it's doubtful he did it in cold blood. The ...

That always killed me. Daniel-San somehow learns karate from all of this, while Miyagi ... Why did The Rich Guy devote weeks of his life to destroying Daniel-San and Mr. Miyagi?

Mr. Miyagi is an important figure in the Karate Kid universe, so it's only natural that Karate Kid: Legends would try to commemorate his legacy.