Nikkei Slides Again on AI Bubble Fears as 5ch Traders Wail: ‘¥4 Million in Paper Losses’

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The story

On the night of Sunday, October 18, 2026, a thread about the Nikkei average on 5ch’s “Nandemo Jikkyo G” (Live Broadcast G) board drew reactions from investors bracing for a steep continued drop on Monday. Rising bond yields at CoreWeave, the GPU-rental company that bankrolls much of the AI investment boom, were flagged as a sign of an “AI bubble bursting,” and posters holding semiconductor stocks like Kioxia reported paper losses topping 3 million yen, with some fearing it could hit 4 million yen by the next day. Still, some cooler heads argued the CoreWeave story was nothing new, and opinions diverged sharply between those sitting on NISA (tax-free investment account) gains over whether to sell, and those who’d only just started investing this year wondering how to respond.

What people said

1AnonymousOct 18, 2026 20:27
Woo-hoo!!!
3AnonymousOct 18, 2026 20:27
Well yeah, just look at after-hours trading and you'll see it coming
5AnonymousOct 18, 2026 20:29
We're in a phase now where stocks just don't go up anymore, so holding just means watching your assets shrink
Surely nobody's still slow enough to not have sold their NISA by now, right?
7AnonymousOct 18, 2026 20:29
Me, a Kioxia holder, can't stop shaking 😰
Already down 3 million yen on paper. Tomorrow it'll probably hit 4 million 😭
10AnonymousOct 18, 2026 20:31
Re: #7
In 10 years you'll be in the green, trust me
8AnonymousOct 18, 2026 20:30
Talking stock prices in the middle of a downtrend like this
is peak uninformed-investor behavior
16AnonymousOct 18, 2026 20:32
Re: #10
I'm on margin though, think I'll be okay? 🥺
19AnonymousOct 18, 2026 20:34
Ever since Trump started that war, I stopped even looking at my P&L
22AnonymousOct 18, 2026 20:34
There's no way margin positions hold up from here
My condolences.
23AnonymousOct 18, 2026 20:35
If you don't get out now, you'll end up hanging yourself…
25AnonymousOct 18, 2026 20:35
Re: #12
People are saying it's an AI bubble bursting because bond yields rose at CoreWeave, a company that leases out GPUs
But that's old news by now, and even if CoreWeave went bankrupt, AI investment wouldn't just stop — yet somehow the market's tanking anyway
35AnonymousOct 18, 2026 20:40
Re: #25
The yield rose because bonds got dumped once interest costs started outpacing profit growth — that's not 'old news,' it's a different situation this time
26AnonymousOct 18, 2026 20:36
Re: #21
What are you even implying 🥺
By the way, I just put in another market buy order for Kioxia
47AnonymousOct 18, 2026 20:57
Re: #26
You're lying, right? lol
27AnonymousOct 18, 2026 20:37
All I can think about is what to buy
30AnonymousOct 18, 2026 20:38
Re: #27
What are you buying?
I want to pick up more Fujikura and V Technology if they drop another leg
38AnonymousOct 18, 2026 20:40
Re: #30
Fujikura's the one I'm watching closest
Kioxia's probably still got a lot further to dig down, so I'm leaving it alone
32AnonymousOct 18, 2026 20:39
Should be fine until the war ends
The question is when it ends, and how
that's the real issue
33AnonymousOct 18, 2026 20:40
Is my Kioxia position beyond saving at this point?
36AnonymousOct 18, 2026 20:40
Re: #33
Yeah, it's pretty much hopeless
Get out on the next pre-earnings bounce
34AnonymousOct 18, 2026 20:40
The whole situation has changed now
There's nothing left to do but sell everything
39AnonymousOct 18, 2026 20:41
Should I cut my losses on my NISA account?
I'm still up 5 million yen right now though
97AnonymousOct 18, 2026 21:33
Re: #39
Depends on your risk tolerance
If you can wait it out for another rally, just leave it be
40AnonymousOct 18, 2026 20:42
Re: #35
Even if CoreWeave goes bankrupt, AI investment isn't going to stop
42AnonymousOct 18, 2026 20:44
Re: #40
It's happening because the market's judging that fundraising will slow down overall now that they have to issue high-interest bonds to raise capital
44AnonymousOct 18, 2026 20:45
Outside of semiconductors and SoftBank, things probably won't get hit that hard
Defensive stocks might even go up, if anything
49AnonymousOct 18, 2026 20:58
Re: #44
Yeah, there were even some defensive names that rose during the last crash
53AnonymousOct 18, 2026 21:00
The door to [painful] 'memories' is creaking open….. (a meme nod to flashbacks of past market crashes)
54AnonymousOct 18, 2026 21:00
Re: #53
Isn't that a 'gap' (window), not a 'door'? (in Japanese stock-chart jargon, a price gap is called a 窓, literally 'window')
62AnonymousOct 18, 2026 21:04
What's going to happen tomorrow???
63AnonymousOct 18, 2026 21:06
Re: #62
I think it might turn into a Black Monday
73AnonymousOct 18, 2026 21:15
For the past several years, everyone who bought the dip came out on top — what's the basis for saying tomorrow's different?
79AnonymousOct 18, 2026 21:18
Re: #73
Tomorrow the Nikkei's going to break below the support line it's been building since July
There's a real chance it keeps sliding over the next month or so and drops below 60,000
Even buying the dip tomorrow would be an awkward position
But it should climb back up again by year-end
77AnonymousOct 18, 2026 21:18
But honestly, the AI bubble's been nothing but harmful at this point, so it's probably better if it just ends
98AnonymousOct 18, 2026 21:33
Re: #77
Exactly
It's all downside
86AnonymousOct 18, 2026 21:23
I got in super late and only started my NISA in September — is now actually a good time to buy, maybe?
87AnonymousOct 18, 2026 21:24
Re: #86
Just hold off a bit longer
Till around December
89AnonymousOct 18, 2026 21:25
My JX Metals position is already dead weight
Should've cut my losses around -25%
93AnonymousOct 18, 2026 21:29
Re: #89
I cut my losses at 2.5 million yen

Background and Key Points of This Discussion

At the heart of this discussion is the rise in bond yields at CoreWeave, the GPU-rental company underpinning the AI investment boom. Posters in the thread noted that the yield increase stemmed from bondholders dumping the debt after interest costs began outpacing profit growth, splitting opinion between those who saw it as “old news, nothing to be surprised about now” and those who argued “this time it’s qualitatively different, since profits aren’t keeping up with interest burdens.” Another point of contention was the differing positions of investors using NISA (Japan’s tax-free investment account): those already sitting on unrealized gains versus those who’d only started in September of this year and suddenly found themselves facing a downturn disagreed over whether to sell or hold. One forecast floated in the thread — that the Nikkei would break its support line and fall into the 60,000-yen range — should be treated with caution, as it is strictly an anonymous poster’s technical analysis, not a confirmed outlook.

*This article is compiled and summarized from the 5ch (Nandemo Jikkyo G) thread “Nikkei Average Stock Price — Four Digits Guaranteed by Tomorrow“.

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