What's going on with "The Reanimator's Sword"?

(Spoilers for Junji Ito's "The Reanimator's Sword.")

"The Reanimator's Sword" begins with our protagonist, Keiji, wandering through the woods with his friend, Murase. Keiji's grandfather is dying and he is supposed to be at the hospital, but instead, he's out looking for human souls. Soon enough, they see a swarm of human souls passing overhead. Keiji follows them to a shrine where he sees a dude blowing white as the human souls smash into his body. The dude sees Keiji watching him and decides to kill Keiji for it—no witnesses. Keiji tries to run, and in his flight accidentally jumps a guard rail right over a cliff. He ends up in the hospital where he witnesses the dude from the shrine reanimate his grandfather—apparently Keiji's father, Representative Soga, knows this guy.

Afterward, Keiji returns to the shrine, meets the dude there again, and confronts him. The dude tells Keiji that Keiji has the potential to be a reanimator just like him—but to use that power, he needs the Reanimator's Sword, and the shrine dude is not willing to share. Keiji refuses to join him, and declares that reviving the dead is "a sin. Maybe worse than murder." But the shrine dude doesn't want his allegiance—Keiji is a threat to him, not a protege. The dude claims to have reanimated Keiji's mother when she died while pregnant with Keiji's younger brother, Jiro. The dude says Keiji died when he fell off the cliff and that he revived Keiji. Keiji kills the dude, knowingly undoing his resurrections. His grandfather and mother and a person who might be his younger brother all explode in light, among a bunch of others. The story ends when Keiji swears fealty to the sword and declares himself "a proud reanimator."

I'm not sure what to make of this story. It's interesting, and it feels like it could mean something, but I have no idea what. If the reanimator represents something, what is it? Fate? What does it mean that Keiji kills the reanimator and assumes his role? What does it mean that he sacrifices his mother, brother, and grandfather?

I notice the human souls kind of look like drawings of sperm. And there's the sword that's used to direct them into a body. That's suggestive. But it's not obvous to me what that adds to the story.

Also there's this random panel on page 161 of Deserter showing this bamboo contraption I've seen before where one piece pours water into the other which then empties out. I know I've seen this before and there's a term for it but I forget what it's called. What is that panel doing there? They're not in a garden at the time, they don't seem to be anywhere near one. What is it supposed to mean? It kind of seems to parallel the grandpa having life force poured into him, which life force will presumably then slowly empty out over time. But I've got no idea what it means.

I don't think the renimator can represent fate. It's a superficially close match: He does spare Keiji's life in what seems to be a lucky break, and similarly for his brother and his grandfather. But you can't kill fate to reverse its decisions and assume its job. That's just silly. So fate doesn't make sense here.

I thought I might figure out answers to my questions by writing about the story, but nope, I still don't understand.