When writing English, we need to pay special attention to keep the subjects of every sentence in a paragraph coherent. For example:

"John is an experienced traveler. Japan is a very interesting country. He has been there thirty times.” is considered to be bad writing because the subjects change from “John” to “Japan” and then back to “he”. It is said that writing like this is difficult to follow and thus should be avoided.

But Japanese is a totally different story. Japanese writing usually changes subjects frequently, suddenly and without notice. By without notice, I mean even omitted subjects, i.e. subjects that are not clearly written out, can change in a paragraph. Take a look at the following paragraph in Japanese, which is copied from a famous novel called Tegami, written by Higashino Keigo.

And here is a direct translation without inserting the missing subjects:
"Thank you so much. Really a great person despite young age,” said while giving a gift envelope. Later, took a look and there are three 1000 yen bank notes inside.

I know this English translation sounds strange. I deliberately translate it into English with a Japanese sentence structure to show you what you will read if you read Japanese with an English mindset. Normally, if you read this Japanese paragraph the way you read English, you will assume that the person who gave a gift envelope and the one who later took a look are the same person, while actually these two actions are performed by two different people. In other words, “そういって小さな祝儀袋をくれた” (said while giving a gift envelope) is done by Person A. And the next sentence “後で見る” (later took a look) is done by Person B. The subjects are changed so suddenly, even though both of them have been omitted from Day One. And writing style like this is considered to be good and normal in Japan!

When reading Japanese, we need to have a little common sense. Because Person A has already given the envelop to someone, she cannot take a look later. A better translation into English requires us to insert all the missing subjects, e.g. “Thank you so much. You’re really a great person despite your young age, “ she said while giving a gift envelope to a young person. Later, the young person took a look and found that there were three 1000 yen bank notes inside the envelope.” Simply speaking, you need to have the ability to insert “the young person” before “took a look”.

In “えらいわねえ”, わね is a phrase used by female, so we know that Person A is female. And she clearly tells us that her listener is young (若い), so we know that Person B is a young person.

Conclusion: Discovering the hidden subjects of Japanese sentences is a hard job. And noticing the sudden change of subjects is a harder one. When you encounter sentences that do not sound logical, especially after being translated into English, it is very likely that the subjects have already been silently changed.