Immortal Defense is a story-focused, abstract game in which the main character, K, gave up his physical body, leaving his pregnant wife, for a chance to defend his family and planet from an invading force. There he meets Aa, who becomes his mentor and helps him through the difficult transition. Throughout the course of the game K fails to defend his planet, but then it mysteriously shows up again, and he has conversations with his granddaughter, who he never met, over the course of millions of years -- but is it all real, or is he defending nothing at all, forever?