いけない subtleties and other issues...

[fevrier]

So, the story is about Uika, a girl whose lazy NEET sister Uichi is one day possessed by a demon. The demon is much nicer and more lively than the sister, so when the demon reveals that the Uichi's spirit will ultimately be erased as a result of the possession, Uika agrees to let the demon stay and take over her sister's life. However, as they are flying back to their apartment, (part of the demon's powers) they crash. As a result, apparently, Uichi and the demon are separated in spite of the demon's earlier insistence that such a separation was impossible if both were to survive. Everything back to normal, Uichi suggests that they go home, and the demon agrees, but then Uika says :

うるさいなぁ
Shut up.


大体　悪魔くんがあんな話を深刻ぶって話すからいけないんじゃない　お姉ちゃん普通に戻ってきたよ
According to the story you told in such deadly earnest, you can’t go, right? Sis is back to normal.

いやぁ実際深刻だったんだよ？さっきの一件で宇一のじ我が強まっていなかったらどうなっていたか
Was I really that serious?. If Uichi’s selfhood hadn’t strengthened back then, who knows what would have happened?

The last two bubbles don't make any sense to me. I assume "あんな話" refers to the doom and gloom story he told about him and Uichi erasing each other's spirits, but then why is 話す in the present if it's referring to that earlier incident? And what is the role of いけない　in this context? Is Uika expressing displeasure and saying the demon shouldn't come back with them because of what he said? Or that according to his logic, he should be unable to? Then why is から　there? Please help.

Page:

[mikkih]

うるさいなぁ
Shut up.

大体　悪魔くんがあんな話を深刻ぶって話すからいけないんじゃない　お姉ちゃん普通に戻ってきたよ
According to the story you told in such deadly earnest, you can’t go, right? Sis is back to normal.

いやぁ実際深刻だったんだよ？さっきの一件で宇一のじ我が強まっていなかったらどうなっていたか
Was I really that serious?. If Uichi’s selfhood hadn’t strengthened back then, who knows what would have happened?

(1)
うるさいなぁ is just a complaint, so "Oh, be quiet" or just "Be quiet"is closer to the raw.

(2)
大体　悪魔くんがあんな話を深刻ぶって話すからいけないんじゃない　
= そもそも、悪魔くんがあのような話を深刻そうに話したのが悪い。

* 大体 has various meanings, but this one means そもそも.
* [から]　（in 話すから） is not "According to."
* Which JP txt applies to [, you can't go, right?] ?
* 普通に normally /like nothing happened

(3)
どうなっていたか I would use "could" over "would."

[fevrier]

2.3: I was thinking "ikenai?" But the way you reinterpreted it, it's disapproval on her part, not a potential. Right?

So, is it something like, "you were wrong for having told a story like that so seriously" with the implication that he was lying/mistaken and should feel bad for making her worry? I guess I still don't understand the role of から　in this sentence.

[mikkih]

2.3: I was thinking "ikenai?" But the way you reinterpreted it, it's disapproval on her part, not a potential. Right?

So, is it something like, "you were wrong for having told a story like that so seriously" with the implication that he was lying/mistaken and should feel bad for making her worry? I guess I still don't understand the role of から　in this sentence.

いけない＝よくない bad/wrong

This いけない is not 行けない(can't go).

Usage of　 ～　から （for ～)

For example:
あなたが/そんなことを言うから/いけないんだ。
You are to blame (It's your fault) for having said such a thing.

悪魔くんが/あんな話を深刻ぶって話すから/いけないんじゃない　 has a similar sentence structure. (じゃない =　でしょう）