Can't Live Without You in Literature.
- The Camp Half-Blood Series: Inverted in Percy Jackson and the Olympians: Instead of a person being dependent on an object, it's the other way around — the Labyrinth can't survive without Daedalus.
- Cerberus High: Another Story, which takes place in an Alternate Universe from the first book in which Kazuki does not exist, describes Oralee's subsequent absence by implying that the two of them cannot exist without one another in the same way that light cannot exist without darkness.
- In the Chaos Gods series, a ritual called a Binding allows two people to share their souls and energies. This allows each to draw upon the strengths of the other; but it also means that if one dies, so will the other. Several important characters are Bound, including Ki's parents and De's parents.
- Dragonriders of Pern
- The dragons are symbiotes who literally can't face life without their rider: a dragon who fails to find a compatible rider upon hatching will die. If they bond to a rider and the rider dies, the psychological trauma causes the dragon to cross the Despair Event Horizon and commit suicide. The only exception is a queen dragon whose rider dies while the dragon is waiting for eggs to hatch — she'll wait until just before Hatching to go Between, and in the intervening time she won't leave her eggs, even to feed herself.
- The riders don't fare much better if their dragons die. One rider went Between with the above-mentioned queen dragon since the queen dragon's rider was riding the first rider's dragon (an older queen dragon) and they made the fatal mistake of going Between when they were already exhausted from doing so multiple times. Other riders in the series have been reduced to a child-like state (Kylara) or have been driven insane with rage (T'Kul). Going through the rest of their lives as shadows of their former selves devoting themselves to other causes to remain sane (Lytol and Brekke) is the best case scenario.
- In The Fire's Stone, to ensure Aaron doesn't run off or otherwise kill Darvish, his soul is linked to the prince's so not only will they die together, but they can't even get very far from each other.
- Inverted in Harry Potter, as the prophecy in the fifth books points out, "Neither can live while the other survives." However, you could say that it is played straight, as Harry is an unintentional horcrux. When Voldemort kills him, he seals his own death.
- Humans and their daemons in His Dark Materials. A slight variation, in that it is possible to separate a daemon from their human with specialist equipment. In this case, both survive, but both are reduced to shadows of their former selves, as the daemon represents the human's soul. Separating them by any other means is fatal to both.
- In the Honor Harrington novels, it is common for bonded treecats to suicide after their human partner, or treecat romantic partner, dies. Since the natural lifespan of a treecat is considerably longer than that of a (pre-prolong) human, the bonding pretty much meant that bonding with a human meant that the treecat would sacrifice many decades of their lifespan. It is also stated that a human whose 'cat dies is likely to give up on their own life as well.
- In Howl's Moving Castle by Diana Wynne Jones (and the film of the book by Hayao Miyazaki), a magical contract binds Howl and Calcifer together. So, as is often referenced when Calcifer talks to Sophie, "If I die, Howl dies too."
- In Midworld and it's semi-sequel Mid-Flinx, the titular Midworld is home to a Lost Colony of people who have become symbiotically linked to the planet's world-spanning forest to the point where each of them is bonded with a native species called a furcot, which resembled a six-legged, tusked bear. When one dies, their partner always dies soon after.
- Due to plot complications involving the source of his agelessness, the eponymous protagonist of the German pulp series Professor Zamorra has recently (as of this writing) become dependent on his friend Rhett Saris not so much to stay alive as to keep his youth; without him, he would revert to his actual chronological age, which while not actually enough to kill him — the series hasn't run quite that long yet — probably would force him to retire from fighting the various forces of evil. (This is complicated by the fact that Rhett himself might yet end up turning into a fairly major demon himself if one of Hell's long-term plans is ever allowed to reach fruition... and they both know it.)
- In the first Neogicia novel, Saly, the protagonist undergoes Bio-Augmentation and wakes up with a second level of consciousness that seems to have developped to avoid sensory overload. In the second, it turns out to be actually be an entity using her as host body, which fills very specific critera seldom found in the general population. That entity is ready to go to lengths much greater that what Saly would consider acceptable to keep her alive and can take over in an emergency. The fact the entity does sensory overload prevention in Saly even when dormant creates an downplayed mutual need.
- The Maternity Spell in the Sword of Truth series does this as part of its Synchronization effect. It links the caster and the target such that whatever physically happens to one happens to the other — if the caster is punched in the nose, the target gets a nosebleed. So if the caster is killed...
- In Watersong, there must always be four sirens, and they must always remain close to one another. If one of the sirens spends more than a few weeks away from the others, or if a siren dies without being replaced by the next full moon, all will perish.
- The Wheel of Time: Aes Sedai and their Warders have a Downplayed version of this bond. If a Warder kicks it, the Aes Sedai will be hit with pretty fierce depression, occasionally bordering on suicidal. Warders who lose their Aes Sedai generally go whole hog, becoming Death Seekers against either the person who killed their partner or just whatever's at hand. It's very, very difficult to keep a surviving Warder alive, and it almost always requires extreme measures.
