The kami are counted at eight million, which is a way of saying they are not counted. That is the first structural fact: the pantheon is open at the edges, and every mountain, river, shrine, exceptional tree and notable ancestor can hold one.
The second is that a genealogy was laid over this openness. The Kojiki begins with heavenly deities, moves to Izanagi and Izanami and their generation of the islands, and arrives at the descent of the imperial line from Amaterasu. That line is the spine of the written mythology and the justification for a dynasty, and it does not describe how kami were actually venerated across the provinces.
Whether Amaterasu heads the kami generally is genuinely arguable. She heads the imperial account, and that primacy was pressed hard during the period of State Shinto. Local cult has always had its own centres of gravity, and Inari and Hachiman have far more shrines than any reading of the Kojiki would predict.
Succession is by delegation rather than conflict. Izanagi, returning polluted from the land of the dead, purifies himself, produces the three noble children, assigns them their domains and passes from the narrative. There is no war between generations of kami.
The door from human to kami is wide and has been used repeatedly. Sugawara no Michizane, exiled and dead, was enshrined as Tenjin after disasters were attributed to him. Tokugawa Ieyasu was enshrined at Nikko. Enshrinement of the dead is a live institution rather than a closed mythological episode.