In an anime there is this exchange:



I know that とは限らない means "not necessarily", and from here I think とも限らない has the same meaning, beside being milder and indirect. Looking around, I found that ないとも限らない means "might", which fits with the idea of とも限らない meaning "not necessarily" (ないとも限らない as "might", minus ない, gives "might not").

All of this seem coherent with the idea if とも限らない meaning "not necessarily", but then I read the quoted exchange, and I'm not sure what it should mean:

But don't push it. You don't have any real experience with Akatsubaki. Not necessarily any issue could arise all of a sudden

Which sounds odd to me: as a warning, I would expect something like "Any issue could arise all of a sudden", which stresses the danger of such issue happening.

I think that "might" and "might not" are not so far, as meaning, since something that might happen could also not happen, and using "might" just stress the possibility it does happen; but I'm not sure if there is something else.

Is this all that's happening, a simple stress on the fact that issue could not arise (but they could, nevertheless)? Or am I missing something?

  • 3
    It's indeed odd. I would expect to see 出ないとも限らない there. It could be a misuse by the author.
    – aguijonazo
    Nov 18, 2021 at 16:40
  • 1
    Agreed with @aguijonazo. Also if this was from an anime it would be in spoken form, which naturally tends to have more slight miscues than written word; it could simply have been misspoken by the voice actor which was either not caught or judged too trivial to do a re-take.
    – Gene
    Nov 18, 2021 at 18:54

2 Answers 2


I have not been able to find any conclusive evidence to suggest one way or the other, but I personally feel it is a misuse, or to be precise, a mix-up of two similar constructs, namely [V ない-stem]-ないとは/も限らない and [interrogative] [V dictionary form]-とも限らない.

This page specifically mentions the latter usage with examples, as follows.




One user on chiebukuro, whose answer was not chosen as best, goes further to claim only いつ津波が襲ってくるとも限らない is grammatical and いつ津波が襲ってこないとも限らない is not, contradicting the best answer.

If these are accurate, the question is whether 何かしらの in your sentence qualifies as an interrogative.


I don’t think it does because it just means “some” and is not asking “what.”

We might get a grammatical sentence by replacing 何かしら with 何, or by adding いつ.



I am not very sure, though.

  • Thanks! What 不知何时死 means? I tried looking around, but came out empty-handed.
    – Mauro
    Dec 31, 2021 at 8:55
  • 1
    @Mauro - That's Chinese. I guess it means, well, いつ死ぬとも限らない.
    – aguijonazo
    Dec 31, 2021 at 8:59

The both 出るとも限らない / 出ないとも限らない sounds the same to me(Japanese native) in this context.

I suppose that this is because it implicitly contains bipolar conclusions. i.e. 出るとも出ないとも限らない (We can't say either "it happens" or "it doesn't happen")
The particle 「」 basically has meanings like too, also, both. Coupled with the negation 限らない it negates the both conclusions, happen and not happen.

However, we would never use 出ると限らない in this context whereas 出ないとは限らない is possible.
I suppose that this is because in many cases the particle 「」 contains a meaning like Against your expectation, You may not know. (Note that there are exceptions)

I think you think it happens, but it's not necessarily so

I think you think it doesn't happen, but it's not necessarily so

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