Why did Sakuta's wound start bleeding again?


In the last episode, when Kaede got her memories back, Sakuta went out
screaming and crying, and his wound started bleeding again. What was the
reason of that bleeding?




While the speculative [answer](https://anime.stackexchange.com/a/50407/31815)
by [@najayaz](https://anime.stackexchange.com/users/35449/najayaz) is
excellent, the movie _Seishun Buta Yarō wa Yumemiru Shōjo no Yume o Minai_
(Rascal Does Not Dream of a Dreaming Girl) provides a different explanation.
Not surprisingly, it involves Sakuta's first crush Shoko Makinohara —
specifically, it ties in with why there are apparently two of them, and why
there's apparently a connection between Sakuta's wound opening and the
appearance of the older version of Shoko.

> The younger Shoko Makinohara will receive a heart transplant in the near
> future, and that heart will actually belong to Sakuta. Due to Shoko's
> puberty syndrome, an older version of her exists due to some time-travel /
> relativity shenanigans. Sakuta's chest wound exists — and opens up whenever
> the older Shoko is nearby — because of the paradox of two of his hearts
> existing in close proximity.

How this situation is resolved forms the plot of the movie.

