Help with subject identification and conversational grammar

Question

いや あいつがさ 不可視境界線だっけ... それを探すって聞かなくってさ... 付き合ってただけだって

I have trouble understanding the grammar in this informal conversation (all said by one person). What I could process (whether correctly or incorrectly) was:

いや あいつがさ 不可視境界線だっけ = No, that person (sa as an emotive particle), 不可視境界線だっけ (<-- joggling of speaker's memory)

それを探すって聞かなくってさ = (that person) says she will look for that, but i didn't hear it (???? this is where it starts to make no sense to me)

付き合ってただけだって = (someone, i don't know who it's supposed to refer to) only accompanied

As you can see, I am really confused as to how this conversation breaks down and also how to identify the subject/object properly in conversation.

Any help will be appreciated.

Thank you!

Answer 1

「いや あいつがさ 不可視境界線{ふかしきょうかいせん}だっけ... それを探{さが}すって聞{き}かなくってさ... 付{つ}き合{あ}ってただけだって。」

Grammar first.

Main clause: 「付き合ってただけだって」

Sub-clause: 「いや あいつがさ 不可視境界線だっけ... それを探すって聞かなくってさ... 」

The subject of the sentence, naturally, is either mentioned or unmentioned in the main clause, agreed? The subject here is the unmentioned speaker.

The main clause means "I was only keeping あいつ company." It ends in a somewhat emphatic quotative particle 「って」. What is left unsaid after that would be something like "I'm telling you", "trust me", etc. If you are already reading something like this, I am sure you have encountered many sentences ending with quotative particles before.

Next, vocabulary.

You totally misinterpreted 「聞かなくってさ」 by guessing its meaning as "I didn't hear it".

「聞かない」 here means "(someone is) so stubborn (that he won't take any advice)". It is a very common word (to describe how kids are, especially). 「あいつ」 is the 聞かない guy here, not the speaker.

「探すって聞かない」 thus means "he is stubbornly determined to look for (it)"

「不可視境界線」 seems to be a newly coined word (for manga/anime?) that means "Ethereal Horizon". As a non-otaku, I will just leave it at that.

All in all, the sentence would mean along the lines of:

"You know, he was so stubborn with the idea of searching for the.. whatcha call it, the Ethereal Horizon? - so, I was just keeping him company."

If I were a Japanese-learner (which is a strange thing to say because I will never be one), I would try to look for the main verb of the sentence and work my way from there. Here it is 「付き合ってた」. And then, I will try to make sure I am getting the correct meaning of every word used.

Answer 2

In some context, it can be different though, the subject of それを探すって聞かなくってさ... should be "あいつ" since in this context "探すって"　is normally interpreted as being shortened by 探すって言って. So, it should mean she wouldn't listen because she wanted to look for it

"不可視境界線だっけ..." is the object of "探す". Now, 不可視境界線だっけ... is a little bit unclear though, I'd interpreted "in the speaker's memory" as what you described like: "What's that? I think 不可視境界線 or something like that..."

Lastly, "付き合ってただけだって" is the what the speaker was actually doing. So, its subject is "the speaker". Anyhow, the speaker ended up hanging around for "不可視境界線だっけ" with "あいつ".