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 [duplicate]

Question

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

Answer 1

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.

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).

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.