てっきり「知らん」ってほっておくものとばかり… I can't understand the meaning of ばかり here


I was reading a manga, and I came across that sentence and I can't understand
the use of ばかり, I read some grammar guides but I can't find an explame or
explanation that fits this sentence. I understand something like [only people
who doesn't want to get involved surely says "I don't know her"]. It's a bit
confusing to what it is referring. If someone can parse it, I would be really
glad.

The context is that a girl runaway and she left a letter, and she seems to
have some problems so she went over to help or something like that. And the
main character is reading the letter and he says that while reading it




This ばかり means "nothing but", and the meaning is applied to the quote marked
with と. Something like 思っていました is omitted at the point of the ellipsis.
(てっきり)～と(ばかり)思っていました is a common pattern that means "I believed ～(, but I was
wrong)" or "I was under the (wrong) impression that ～". See [these
examples](https://j-nihongo.com/tekkiri/).

You have overlooked many grammar points of this sentence.

  * てっきり by itself means something like "without doubt", but it is a guiding adverb that is **always** followed by the speaker's wrong assumption, so (ばかり)思っていました is often omitted when てっきり is already present. Sometimes the assumption part itself can be omitted.

> てっきり今日は月曜日だと!  
>  I believed it was Monday today (but I was wrong)!
>
> 僕はてっきり!  
>  I was completely mistaken!

  * This 知らん is "I don't care" rather than "I don't know".

  * ほっておく is short for 放って【ほうって】おく, meaning "to leave alone" or "to let go".
  * ものだ is used because the speaker thought 放っておく was the natural choice based on the speaker's experience/knowledge (see [this](https://japanese.stackexchange.com/a/29018/5010)).

Therefore:

> てっきり「『知らん』ってほっておくもの(だ)」とばかり(思っていました)。  
>  (literally) Without doubt, I was just thinking "naturally, you will leave
> her (saying) 'I don't care'".  
>  → I was under the impression that you would certainly ignore this and leave
> her alone.




This ばかり means "nothing but", and the meaning is applied to the quote marked
with と. Something like 思っていました is omitted at the point of the ellipsis.
(てっきり)～と(ばかり)思っていました is a common pattern that means "I believed ～(, but I was
wrong)" or "I was under the (wrong) impression that ～". See [these
examples](https://j-nihongo.com/tekkiri/).

You have overlooked many grammar points of this sentence.

  * てっきり by itself means something like "without doubt", but it is a guiding adverb that is **always** followed by the speaker's wrong assumption, so (ばかり)思っていました is often omitted when てっきり is already present. Sometimes the assumption part itself can be omitted.

> てっきり今日は月曜日だと!  
>  I believed it was Monday today (but I was wrong)!
>
> 僕はてっきり!  
>  I was completely mistaken!

  * This 知らん is "I don't care" rather than "I don't know".

  * ほっておく is short for 放って【ほうって】おく, meaning "to leave alone" or "to let go".
  * ものだ is used because the speaker thought 放っておく was the natural choice based on the speaker's experience/knowledge (see [this](https://japanese.stackexchange.com/a/29018/5010)).

Therefore:

> てっきり「『知らん』ってほっておくもの(だ)」とばかり(思っていました)。  
>  (literally) Without doubt, I was just thinking "naturally, you will leave
> her (saying) 'I don't care'".  
>  → I was under the impression that you would certainly ignore this and leave
> her alone.

