To Infinity and...Behind? (слэш)

Time travel wasn't supposed to work like this. He'd done the calculations himself. It shouldn't be possible for them to be in their own past. They were supposed to end up in a different-yet strikingly similar-universe because True Time Travel doesn't exist. But now they have apparently replaced their former selves and there was no 'Future' to get back to. There was only the here and now which just so happened to be 11 years in the past.
"Tony was starting to hyperventilate. Which did not help when he realised that the particles he was breathing in were actually him. In fact it made everything 10 times worse.
“Oh my god. This is-I can’t.” Tony gasped. “I accidentally killed myself. This is like legit suicide.”
Bruce winced but still reached out for his friend. He grabbed Tony’s shoulder and tried to ground him. “Actually I think suicide requires intention and we definitely didn’t mean to do this. So this is more like accidental death.”
“So I accidental deathed myself to death. How comforting.” "