Half & Half is the debut manga of Seo Kouji from 1996, reprinted in 2007 and expanded in 2012-2015 into a 13 chapter series.
Nakagawa Shinichi was minding his own business when the crowd around him grows agitated and he looks up, seeing a girl falling from a building and right on top of him! Both Shinichi and the girl, Senada Yuuki, die during this accident but find themselves surrounded by white light. A voice tells them that they'll be given a time-span of 7 Days to live again, but after the time is up, one of them must die.
Now Shinichi and Yuuki must start to get along because they now share a life, meaning they cannot be apart from each other too far or they will both instantly die, as well as sharing a symbiotic link where they experience the other's emotional and physical feelings. As the days tick by and both want to live, how will Shinichi and Yuuki work around this issue? And what will happen at the end of those 7 Days?
Half & Half Contains Examples Of:
- A Date with Rosie Palms: Averted. Yuuki forbids Shinichi to masturbate for the duration of their 7 Days because their Psychic Link means she feels it, too, and she hates it.
- Babies Ever After: In the final chapter, Shinichi decides that he will die upon realizing that Yuuki is pregnant with his child. After a Time Skip, we see Yuuki living with Shinichi's father and grandmother with her son Shinji.
- Bait-and-Switch: The last chapter at first makes it seem like Shinichi survived before revealing it was Yuuki.
- Bungled Suicide: Shinichi and Yuuki decide to commit double-suicide by jumping off a cliff... but fail because of an unwritten rule.
- Childhood Friends: Shinichi's best friend Kiyoharu. They've known each other from childhood. And then it's revealed Kiyoharu been sleeping with his girlfriend.
- Dead Guy Junior: Yuuki names their son Shinji (written with the Kanji for 'two') after Shinichi (written with the Kanji for 'one').
- Four Day Romance: Yuuki and Shinichi fall in love and sleep with each other after about 5 days of knowing each other. Justified, they only have 7 Days with each other and don't have time to waste by stuttering around each other.
- I Cannot Self-Terminate: Shinichi and Yuuki must remain alive for all 7 Days that they have, they can't die before, which they realize when they try to commit double-suicide.
- Psychic Link: Shinichi and Yuuki share the same feelings, whether it's something emotional like sadness or physical like pain.
- Someone to Remember Him By: Yuuki was impregnated by their night of passion and that was the reason she survived.
- Someone Has to Die: Either Shinichi or Yuuki must die after the 7 Days are up.
- Starts with a Suicide: Yuuki's suicide and her landing on Shinichi starts the story off. It's later revealed that Yuuki was pushed.
- Take a Third Option: Subverted. Shinichi tries to take the third option of "both die" and "both live", but is told that it's impossible and only one of them must, and will, die.
- 13 Is Unlucky: The series is concluded with 13 Chapters, with the death of one of the protagonists being the main event.
- Time Skip: The last few pages of the final chapter take place a few years after their 7 Days are up.
- Your Cheating Heart: Shinichi and Yuuki stumble on his girlfriend cheating on him with his best friend, their reason being that nobody would believe their story on why the two are together. Though it's implied it's not the first time they've slept together.
- Your Days Are Numbered: The voice that allows Shinichi and Yuuki to survive gives them 7 Days to live before one of them has to die.