Can't Live Without You in Anime and Manga.
- Ah! My Goddess has the doublet system, in which random pairs from heaven and hell are linked. If one dies, the other dies. After they are linked, their memories are erased — the purpose being so if you kill someone on the other side, you don't know which of your allies would die (it could be you, natch).
- Arthur and Shalott in Air Gear; Shalott was almost killed when another character kicked through his chest, damaging all his vital organs, so Arthur's organs were transplanted into Shalott. Now Arthur has no organs, so he's dependent on a literal blood connection between him and Shalott for feeding and waste elimination, and will die in a couple hours if the connection is interrupted.
- In one chapter of Black Jack, the title doctor surgically attaches a young boy with lungs weakened by heart disease to his mother until he can get an organ donor.
- Bleach: The filler Bount arc features Dolls, the Bounts' Empathic Weapon. Similar to Zanpakutō, but the Bount and Doll are more linked; if one dies, so does the other.
- Elraine and Kiri of Double Arts, must always be physically touching (normally holding hands) or Elraine will die of the disease she's infected with but he's immune to and staves off.
- Dragon Ball:
- Dragon Ball Z:
- If Piccolo were to die, then Kami would as well and vice-versa. This is because they were originally one person but Kami cast off his evilness in order to become guardian of Earth. That evilness turned into Piccolo. On the plus side, you only have to resurrect one to get both back. This is no longer an issue once the two of them fuse back into one being.
- Shenron and Porunga also cease to exist (and their respective Dragon Balls turn to stone) if their creator dies, though the connection can be passed on before the creator dies (and the dragon can even be recreated after if the original materials are found). For Shenron, that's Kami, later replaced by Dende after Kami fuses with Piccolo. For Porunga, that's Grand Elder Guru, later replaced by Elder Moori after Guru passes away.
- Dragon Ball Super:
- Similarly, it's revealed that if the Supreme Kai of any universe were to die, so would a God of Destruction of that universe. The reverse is, presumably, true. Goku surmises that he could defeat the latter if he defeated the former, but then decides that wouldn't be any fun. Beerus is less than amused.
- Whis also cannot exist without a God of Destruction around, so if Beerus dies, Whis will cease to function until someone else takes up the role. This is probably why he asked Goku and Vegeta if they wanted to replace Beerus if he dies, as a backup plan for if it happens.
- Dragon Ball Z:
- This is the case for Eureka in the Eureka Seven. She was born from Scub Coral as a Human Coralian and whatever damage done to the Scab Coral, Eureka also feels it as they are synced. If the Scub Coral dies or disappears, the same fate will happen to Eureka, which served as a major motivation for Renton to fight for Humans and Scub Coral's co-existence.
- In the movie ending, Eureka was reborn as a human being and lost her memories. She stated that she could only exist as long as Renton lives and dreams.
- Fairy Tail: Since the Books of Zeref channel their creator's magic, if Zeref were to die, the Etherious will die with him. This includes E.N.D., which is why Happy prevents Natsu from landing a possible finishing blow on his brother/creator after learning the truth of his origins.
- Inuyasha: According to Naraku's final detachment Byakuya, even if his other "siblings" had survived, they would have perished if/when Naraku was destroyed anyway.
- At the afterword section of chapter 660 of the web novel I Was Caught up in a Hero Summoning, but That World Is at Peace, Shiro's blessing for MC Kaito has evolved to grant him absolute immortality, as long as the God of Creation herself exists.
- In Reborn!, one character, Chrome Dokuro can live only because her organs, the originals of which have been removed, are physical illusions cast by Mukuro Rokudo.
- Mizumi of Return to Labyrinth can remove an aspect of a person's personality to make a clone but if the original dies, then so does the clone and vice versa.
- Sailor Moon: If the Maijuku dies, Al and En go down as well. Or as En's DiC Entertainment dub counterpart explains, "if the Tree dies, ALAN, we die!"
- Sequence, by Saenagi Ryou, starts out with the main character, Kanata, accidentally freeing a young imprisoned vampire, and getting his heart ripped out for his trouble. The vampire, who isn't actually a bad person, ties their life forces together to keep Kanata alive.
- Fai and Kurogane in Tsubasa -RESERVoir CHRoNiCLE-; the former can't live without the latter, since, as a vampire, Fai's dependent on blood for feeding, and can only feed on Kurogane.
- Charlie in Vassalord is a vampire who is dependent on blood from his master Rayflo because, due to Charlie's religious views, he refuses to drink from humans since he sees it as a cardinal sin. (Drinking from Rayflo is also a sin, but in Charlie's eyes it's the lesser of two evils.)
- In The World God Only Knows, Elsie and Keima share collars/chokers that dictate that if one dies, the other will as well, no matter what they die from.
- Vermeil in Gold: After she accidentally stabs Alto through his heart while on a berserker rampage (induced by Professor Obsidian), Vermeil is forced to link her own heart with his to keep him alive. Alto objects to this, since humans have shorter lifespans than demons, but she's fine with it because it's not like she would have any other reason to live if he dies.
