Dude, Kira is not a thing, person, or single entity. Kira is the will of many brought forward by one. Kira was obviosly smarter than L, hence L's demise. However, your missing the big picture. Who created Kira? It was ME! Ryuk. However accidental it may have been, the Shinigami are the designers behind the plot. Kira is a tool. A means to an end. For anyone who has not seen death note, i would advise reading the manga before watching the anime.