Hi, a few grammatical fixes. :) Otherwise excellent work!

Would you correct following sentences?

This is very good! 大阪にまだ行かなかった、でも行きたい！

* Even though it is clear that the subject of the 作文 is Osaka, you just mentioned Tokyo. So to avoid confusion, I would write "Osaka" instead of "there." However, look what happens if you switch the sentence around:

"I visit there regularly even though I live in Tokyo." (If you arrange the sentence this way, it is clear that "there" means "Osaka" because Osaka was the most recent place that you mentioned).

** There is a lot of debate about when to use "which" and when to use "that." The rules are very complicated, and experts don't agree on them.

"That" and "which" are both used to connect two phrases. ("A that B" or "A, which B").

"A" is the main subject of your sentence. ("I like the unique atmosphere").

"B" clarifies something about the atmosphere, and adds new information ("I can't find this atmosphere in Tokyo")  

In general, if "B" is important for understanding "A" then use "that."

But if "B" adds new, extra information about "A" then use "which."

In your sentence, the "B" part does both. So either one works.

But if you use "which," I recommend that you put a comma before it. The comma makes the reader pause, and it helps show that the words after "which" will provide new information.

In Thabo's correction, he changed "which" to "that" and it improved the sentence. My version (with a comma and "which") has a slightly different nuance. Both are correct.