In Chiikawa's parallel world arc, part of the bug bite story, a tree comes running up to Hachiware and calmly explains a disaster nobody has seen before: what the insect does and how to get home. Here is why that tree is the creepiest part of the story, keeping what the manga shows apart from fan theory.
Spoiler warning: This covers TV anime Episode 378, “Parallel World IV,” aired on September 15, 2026, plus later events from the original manga posts.[1]
Hachiware is walking around a world that feels almost normal but slightly off. Chiikawa has passed the Level 5 weed-pulling exam, has an unusually high monster-hunting rank, and lots of small things have shifted. Then Hachiware spots an insect that looks like the one that stung Chiikawa back in the real world, and chases it. A tree shows up.[2]
Most stories would bring in a scientist, a wise old guide, or a lone survivor at this point.
Chiikawa brings in a tree. A running one.
Then the tree starts explaining the insect's whole life cycle.
You laugh at first. Then it turns into a real question: how does a tree know all this?
The insect is way too dark for this cute art style
Here is what the story tells us, in short:[3]
- The insect plants a parallel world inside someone's head.
- That world mixes with the brain and grows.
- Later, the insect comes back to suck that grown world out.
- The person it feeds on ends up “empty.”
- Anyone who walks into that world can get stuck there for good and become one of its residents.
So it is not just a bug that gives you weird dreams. It grows a whole world inside your brain and then eats it.
And it is not even evil. It just flies around doing what this kind of insect does. You can run from a wild animal or fight a villain. This thing ruins your life simply by living.
If Hachiware hadn't chased the insect, there might have been no way out
Hachiware has no guidebook. Hachiware just notices something is off, suspects the insect has something to do with it, and follows it.[2]
That tiny choice changes everything.
Without it, Hachiware might never meet the tree or learn how to get back. Meanwhile, the real Chiikawa is heading toward becoming “empty,” and Hachiware risks being stuck in the parallel world.[3]
The story never actually says anyone dies. But losing who you are on one side and never getting home on the other is already heavy enough.
The escape doesn't feel like a puzzle solved perfectly. It feels like grabbing a very thin thread by pure luck.
The tree even seems to know when it's too late
The tree tells Hachiware that the insect has to be destroyed to get back.[4] As the story goes on, Hachiware's body starts changing to fit the parallel world.[5][6]
The story never spells out exactly how far the change can go before there's no way back. Still, the tree seems to know about both the risk of getting stuck and the changes to the body.
Knowing “that bug is dangerous” is one thing. You could figure that out by seeing it once. But the tree seems to know what happens to the person with a world planted in their head, what happens to an outsider who walks in, how to escape, and which way the body will change.
Mr. Tree, how many cases did you study to learn all that?
Suddenly the running tree looks less like a joke character and more like the only staff member at the Parallel World Disaster Response Office.
Fan theory: were there victims before Hachiware?
The manga never says the tree has seen lots of victims. What follows is guesswork based on how much the tree knows:
- it has seen the same thing happen again and again;
- someone else passed the knowledge on to it;
- it has watched the insect for a long time;
- it was once an outsider itself and never made it home.
The last idea gets stronger because, during the return scenes, the story hints that the tree once wanted to go back too.[7][8]
Read that way, the tree is less a friendly guide and more like someone who got stuck here earlier, can't leave, but can still show the next lost visitor the way out.
Even so, that doesn't fully explain how it knows so much about the insect.
The parallel world is a trap because it's actually nice
This world isn't all bad. Chiikawa passed the weed-pulling exam and has great hunting results. Some things are going better here than in real life.[2]
That's why Hachiware can't just say “it's all fake, let's wreck it and go home.” Having seen the good side, Hachiware even worries about what will happen to this world once the insect is gone.[4]
That's the clever part. A world where your wishes come true isn't automatically a world that's good for you.
Passing an exam, getting stronger, getting praised: on their own, they all look like success. But if the price is your old body, your friendships, and your freedom to go home, the math changes completely.
A dream job whose benefits package includes “you can never leave” sounds like a terrible employer.
Hachiware gets stronger, in the worst way possible
Later on, the more Hachiware settles into this world, the bigger and more beast-like Hachiware's body becomes.[5][6]
The irony hurts: that stronger body can finally take down the insect with ease, after all that struggle.
Want to be stronger → actually get stronger → your best friend looks at you like a monster to be hunted.
The wish came true in just about the worst way it could.
The power boost is real. But it costs your looks and your friendships too. Getting stronger isn't much comfort if your best friend can barely recognize you.
The more at home you feel, the harder it may be to leave
Because this world has good things in it, it isn't easy to walk away. But the more Hachiware gets used to it and gets stronger, the further the body drifts from the old Hachiware. Settling into a new place is usually a good thing. Here it makes you wonder whether the door home is quietly closing.
The story doesn't make it clear whether the good things came from someone's wishes, or whether wanting to be strong caused the change. What it does make clear: being stronger doesn't help much if your best friend can't tell it's you.
Tree, seriously, who are you?
The insect plants a world in a head, lets it grow, and sucks it out. Hachiware changes shape, uses the stronger body to destroy the insect, and goes back to the real world.[3][6][7]
And the way home was explained by a tree that came running in from the side.
For everyone else it's a first. For the tree, it looks like a disaster it knows by heart.
Has it seen this many times? Was it trapped once too? The story hints the tree wanted to go home, but that still doesn't explain everything it knows about the insect.
I started out worried about a cute little bug. I ended up worried about the tree's past.
Tree, how many times have you seen this happen?
References (8)
- Episode 378, Parallel World IV: video cited by the original article as the 2026-09-15 broadcast youtube.com
- Bug-bite timeline: personal blog linking the original posts chiikawa.hatenablog.jp
- Nagano’s official post: the insect drains the world twitter.com
- Nagano’s official post: how to return twitter.com
- Nagano’s official post: the changing body twitter.com
- Nagano’s official post: the transformed body defeats the insect twitter.com
- Nagano’s official post: the return twitter.com
- Nagano’s official post: ending relevant to the tree’s wish to return twitter.com
