Warning: major spoilers for Mushoku Tensei: Jobless Reincarnation Season 3, Episode 13 “Diary,” and for the web novel material that comes after it.
The Mushoku Tensei rat incident: a rat with purple crystal-like teeth gnaws on food, pregnant Roxy eats some and gets Magic Stone Disease. That starts the failed timeline in Old Rudeus’s diary.
Watch Turning Point 4 and then the diary episode, and you probably think this:
“Future Rudeus came back and nearly killed himself to warn him. Why does Rudeus look like he isn’t listening?”
Then Episode 13 wipes out one person after another: Roxy, Cliff, Sylphie, Eris. It looks like everything collapses right after the warning.
It all makes sense once you put the timeline in order.
Episode 13 is not the future Rudeus gets by ignoring the warning. It is the record of the failed timeline Old Rudeus lived through before he traveled back.[1][2][3]
1. Current Rudeus follows the important warnings
Old Rudeus does not only warn about the basement.
He tells Rudeus to talk to Nanahoshi and to contact Eris. He tells him not to trust Hitogami fully, but not to rush into an unwinnable war either.
Current Rudeus puts all of that into his plan.[2]
He doesn’t just open the basement door, either.
He keeps his family out of the way and checks the rat tracks leading down. He doesn’t open the door. He sends cold magic through a small hole and freezes the room first, then goes in. Inside he finds a rat with purple, crystal-like teeth, just as Old Rudeus described.[4]
So the difference looks like this:
Failed timeline: opens the basement normally → the rat escapes → hell begins
Main timeline: Old Rudeus shows up → the rat is trapped → the first landmine is defused
If you treat Episode 13 as the future that’s coming, Rudeus looks like an idiot.
Think of it as the original save file the strategy guide was made from.
2. Turning Point 4 is one rat, fifty years of ruin, and a time traveler
Hitogami doesn’t send an assassin.
Rudeus goes into the basement. A startled rat runs off. The rat gnaws on food. Roxy, who is pregnant, eats some. Magic Stone Disease begins.[4]
From there it all links up:
Rudeus tries to save Roxy
→ loses Cliff while trying to get god-grade detoxification magic
→ gets back too late and Roxy dies
→ Rudeus breaks down
→ his bond with Sylphie falls apart
→ Sylphie goes back to Ariel’s side and dies in a lost political fight
→ Old Rudeus throws himself into revenge
→ keeps mistaking Eris for an enemy
→ Eris finally dies protecting him
→ decades of research and revenge
→ he invents past transfer
→ he appears before his younger self[4][2][3]
The rat: “Just popping into the kitchen.”
The world: “Got it. Generating a time traveler from fifty years later.”
The butterfly in the butterfly effect turned out to be a rat.
3. Why doesn’t Hitogami just kill Roxy? Fate is too stubborn
Hitogami explains this himself.
Rudeus has such strong fate that no matter how many times Hitogami adjusts the future, Rudeus still ends up meeting Roxy, marrying her and having a child. Roxy, Sylphie, Eris and their descendants have strong fate too.[5][6]
So Hitogami doesn’t set up a “kill Roxy” event. He nudges cause and effect, a little at a time.
He also says a woman’s fate becomes less certain for a while during pregnancy.[5]
So he takes a huge detour:
gives useful advice for years
→ earns the trust of a suspicious Rudeus
→ waits for the weak moment, pregnancy
→ asks him to check a basement that seems unimportant
→ uses a rat to create a death that looks like an accident
Hitogami himself admits, more or less, that most of his earlier advice helped Rudeus, and that it was a way to build the trust he needed for the basement job.[6]
A salesman is scarier than an assassin.
4. Old Rudeus’s rat theory was a guess, and he still got it right
Old Rudeus never saw exactly what happened fifty years earlier.
He says himself that how the rat got in is a guess, and that the clues from the past only came together thirty years later.[4]
Young Rudeus also considers that his future self’s research might be wrong.[2]
Even so, the main timeline lines up:
- there are rat tracks leading into the basement
- the rat has the purple crystal teeth he described
- once the rat is dealt with, Roxy doesn’t fall ill
It may not be “scientifically proven,” but inside the story it comes down to this:
Old Rudeus: “It was probably a rat.”
Reality: “Well, there’s the rat.”
A future self broken by revenge, who also works backward like an epidemiologist.
5. Why Episode 13 kills so many people: a whole bad ending squeezed into one episode
The broadcaster’s official listing describes Episode 13, “Diary,” as the harrowing life of Rudeus’s future self, starting with Roxy’s death.[1]
That is why the body count feels absurd.
Another anime would stretch this over several episodes. Here the diary lets it all pass at once.
Roxy dies
Cliff dies
Sylphie dies
Eris dies
Only Rudeus survives, and turns into a magic-research monster
But Hitogami doesn’t kill all of them directly.
He bends the first cause. From Roxy’s death on, Rudeus’s decisions, his relationships and the political situation all get worse.
That’s the scary part.
Hitogami doesn’t attack with spells. His style is knocking over a single piece of the worst possible domino run.
6. Old Rudeus: his life failed, but his magic evolved into something monstrous
This is the cruelest irony.
After losing almost everyone he wanted to protect, he put decades into revenge and research, and as a mage he went far beyond current Rudeus.
The story shows gravity, lightning, teleportation, magic armor, regrowing a lost arm and, in the end, travel into the past.[4][5]
He says himself that magic in this world has a very wide range of uses, and that once you grasp the principle, you can do far more.[4]
But that isn’t a victory.
By the time he was strong, there was nobody left to protect.
Life build: wrecked
Magic research build: maxed out
The strongest researcher ever, who put every stat point in the wrong place.
7. Did time magic remove his organs? No, his spell was unfinished
Old Rudeus’s past transfer succeeded and failed at the same time.
He did reach about fifty years in the past. He also brought the diary.
But as he admits, the technique was “incomplete,” and he couldn’t bring his whole body.[4]
After he dies, young Rudeus examines the body. There is a huge gap in the abdomen, and most of the organs are gone.[4]
He had also used up all his mana on the transfer, so he couldn’t regenerate.
So there is no rule that time travel makes your organs disappear.
The closer reading is this: Old Rudeus’s first prototype time machine failed to carry a human body.
He even hints that if Cliff had lived, he might have been able to improve the past transfer.[4]
8. Did he see Sylphie and Roxy through the wall, see the future, or hallucinate?
Old Rudeus’s ending is heavy.
He looks at something over young Rudeus’s shoulder and reacts to Sylphie and Roxy. But at that moment, the door hasn’t opened yet. Soon after, the two of them really do come down the stairs.[4]
In the web novel, young Rudeus wonders, “What kind of hallucination did he see?”
Because the two appear a few seconds later, you can also read it as a glimpse of a very short future.
The text doesn’t make clear whether it was seeing through the wall or seeing the future.
Even so, this alone is enough to hit hard:
two people lost for almost fifty years
→ in another timeline, they’re still alive
→ Old Rudeus, about to die, sees that at the very end
Old Rudeus couldn’t save the world. But he could hand his younger self the information needed to build a world where those two are alive.
9. Hitogami vs. Orsted: who’s the real villain?
From here the story leans much harder into Hitogami.
Hitogami isn’t a simple “demon lord who wants to wipe out humanity.”
The motive he gives Rudeus, at least, is self-preservation.
In the future, Rudeus’s descendants help Orsted and may reach him. So he wants to erase that future.[5]
Orsted, on the other hand, makes the worst first impression possible.
He carries a curse that makes most living things fear and shun him. Without doing anything, he already looks like “the final boss, obviously.”[7]
But once Rudeus becomes his subordinate, Orsted keeps his promises, shares information and protects Rudeus’s family.
He is also carrying a long time loop made to defeat Hitogami.[7][8]
In short:
Hitogami: approaches as a pleasant adviser, a long-term manipulator
Orsted: frightening in looks and first move, but quite loyal after the contract
Two characters whose first impressions flip.
Conclusion: Turning Point 4 isn’t just the “rat episode.” It folds fifty years of cause and effect into one door
What makes this stretch impressive isn’t a strong enemy showing up.
All that happens is someone opens the basement door.
And that one action carries all of this:
whether Roxy lives or dies
whether Cliff lives or dies
whether Sylphie lives or dies
whether Eris lives or dies
Rudeus’s personality
the future of magic research
the fight against Hitogami
the alliance with Orsted
and a past transfer from fifty years later
That’s why your first thought is:
“Just don’t open it.”
To make sure he does the one simple thing, Hitogami builds trust for years, Old Rudeus spends his whole life working out the cause, and in the end he leaves his own organs behind to reach the past.
That is too much cause and effect for one rat to carry.
And if Episode 13 made you wonder “why isn’t he listening?”, the show got you cleanly.
It isn’t a future where the warning was ignored. It’s the reason the warning exists.
References (9)
- TOKYO MX: Episode 13 “Diary,” September 20, 2026 mxtv.co.jp
- Web novel Chapter 155 “Diary, Part 1 ncode.syosetu.com
- Web novel Chapter 156 “Diary, Part 2 ncode.syosetu.com
- Web novel Chapter 154 “The End and the Beginning ncode.syosetu.com
- Web novel Chapter 157 “Resolve ncode.syosetu.com
- Web novel Chapter 160 “Preparations ncode.syosetu.com
- Web novel Chapter 166 “Summons ncode.syosetu.com
- Web novel Chapter 187 “The Truth About Orsted and Ten Days in the Capital ncode.syosetu.com
- Official Mushoku Tensei anime story index: Season 3 Episodes 11–12 mushokutensei.jp
