i think the novel and manga endings are different in that respect then. i finished the manga and its very clear that he's on trial by the end and not dead
(novel spoilers)
the manga and novel essentially have the same ending, but there are some differences.
in the novel: (1) the author and yuzuki don't go to the katabuchi house and meet keita (2) the news headlines would say that keita's whereabouts are unknown (3) kurihara mentions in his afterword that it's a coincidence that no one knows where keita is and it was never revealed who the severed corpse in the beginning of the story was. in addition, there wasn't really any proof that it was keita who wrote the letter that was sent to yoshie. thus leading to the speculation that keita was dead from the start and never wrote the letter.
Hello can some novel readers tell me about the ending. Like why do some people in Reddit say that Keita died at the beginning or even keita’s letter is fake and not written by him.