Ai-Ren is a sci-fi elegy for humanity's last days. In the far future, humans have generally lost the ability to reproduce normally, and use technology to patch up the holes left by nature, with quietly mounting desperation. Meanwhile, nuclear war and poverty scourge the global south, until a mysterious stranger arrives to deliver us from total oblivion. This is all takes in place in the background of the main story, where the terminally-ill Ikuru acquires an artificially-made "end-of-life companion" named Ai whose own lifespan is intentionally made short. Their relationship is doomed to end soon, but, like the other characters, they continue to find joy in small things, children continue to be born into this cursed world, and life stubbornly lurches forward, determined to run out the clock. Ai-Ren is a succint and potent reminder that, in a very real way, love is the only thing that defies death.