I don’t think the ending is bittersweet. I think there’s two ways it could go. Minoru told Mary to give him directions in Hell. That means Maru can travel between realms at will. So either they’ll be together in Hell for eternity or Maru will guide Minoru through Hell so he can be reincarnated over and over again.
I don’t think the ending is bittersweet. I think there’s two ways it could go. Minoru told Mary to give him directions in Hell. That means Maru can travel between realms at will. So either they’ll be together in Hell for eternity or Maru will guide Minoru through Hell so he can be reincarnated over and over again.