@Tersione Sorta yes and no. What do you define as natural? A random curse that doesn't target specific people but just hits randomly... can it really be considered unnatural? Or maybe it can be considered in the same vein as a disease or infection. Those can be deemed natural causes after all.
The curse just now seems to exist.
@Kaarme To be fair, this situation isn't pleasant. But that's literally life. Your loved ones could die or other random people could die. Hell, people DO die... it's just rare that you know about it and have the option to stop it.
This is a tragedy for him solely because he could stop it, not because the people die.
If his girlfriend's death wouldn't end things, then this wouldn't be a tragedy. Instead, it'd be her just giving other people more time. The tragedy comes solely because the choice exists.
And while there are a lot of manga like this, it should be noted that there are just a lot of manga. It's like why Isekai seem overboard. Not because it's a huge majority, but because a lot of manga exist. Of course, it gets a lot of attention... because people want to complain about something... but if you look at the whole picture, you'd see that there is a large variety of manga. Just like there are a large variety of books coming out for Western markets, with a large variety of genres and tropes and plots.