This is seinen. So obviously it has more mature plot than regular. But it's not something weird. It's about the eternal love and profound realisation of humanity and peace ; defining human legacy and basic needs. I watched the anime and I feel honoured for this fortune. This contains the best story among all that I read in novels or in manga or watched in films and anime. I swear, you are not going to regret watching the 2 seasons of this anime.