It's basically... all of us have stories we want to tell, either fiction or nonfiction.
Mine's largely fiction, though sort of autobiographical.
I was standing new a church one day, looking at a field of wheat and super-tired. I had this daydream of a girl standing in a white robe, carrying a sword. It was sort of Asian style usually either a katana or a Chinese sword, and the end of the handle usually had a chain tied to it, which had a heart attached, usually broken. The heart, not the chain.
When I wrote an RPG game, Oracle of Tao, this became part of the mythos. The girl became Anideshi, a sort of nature hero, that was cursed with reincarnation. Further backstory says this sword isn't even hers. The sword was possessed by an angel Cassiel (the Angel of Sorrow, of course) but it wasn't made by her. It was made by Yomi, the Reaper of Death, who originally used it as a tool. This doesn't come out until playing my second rpg, Tales from the Reaper. To spoil alot, one of the last chapters, Yomi and Seishii (Reaper of Birth, Reapers in this game are less killers of humansd and more like backstage crew of existence, the garden variety psychopomps are called Pales and are former humans) decide they love each other, and to keep existence from being destroyed, they agree to reincarnate a bunch. Yomi then, is actually Anideshi, which means she is rightful owner of the sword.
Now, about this sword. It's basically a sword that causes death. Hence the name. But it's also a sword of regret, which can revive others from death. And the chain extends allowing it to wrap around stuff.
The Sword of Sorrow, in the myth, actually turns out to be the "source of sorrow" as it is a corrupted phrase. The Sword symbolizes sorrow possessed by its wielder, and its source. What is the source of sorrow, then? In game, it turns out to be loneliness I think. Which is another way of saying that for much of my adult life, I was extremely depressed and viewed myself as cursed with loneliness. The Sword of Sorrow can also turn into a Sword of Love, because it's effectively the feelings of love/loneliness within the heart.
Curiously, besides the games I wrote, the sword actually exists. It's a letter opener! Back when I visited China we brought back a tiny letter opener that was modeled after a chinese sword, and I attached a chain I found somewhere to the other end, along with a heart made of rose quartz I got from part of a pendant. The sword usually tied closed by its own chain. I'll see if I can post a picture. Technically it's Bearer not Wielder, as I've never used this in any way. I also have a legit katana that I could probly get a jeweler or something to attach a long chain to.
Also, there is a Wuxia show online, called Legend of the Ancient Sword. The sword doesn't have any of the same characteristics, but is called the Sword of Burning Solitude. It's close, but this is kinda a fire sword, while the Sword of Sorrow is water and darkness mostly. Still, it's a fun show to watch.