What a mess. They decided to adapt the sequel manga while adapting the first manga through flashbacks. Imagine that kind of bullshit in any other medium, like if they made Return of the King first only to pad out the time with butchered up flashbacks of everything that happened in Fellowship of the Ring and Two Towers.
It also didn't make the premise any less stupid for what's essentially a phone novel. It's all shock value BS with no logic behind any of it.