I have no idea where this question belongs. I hope it’s okay to post it here.
There’s this background music that I’ve heard in at least three different Japanese youtubers’ videos. I’m wondering what it is and why it’s used so often, just out of curiosity.
You can hear it every time there’s discussion in this 日本語の森 video (starting from 2:05)
I don’t know that specific song, but usually when you hear a song a lot in Youtube videos it’s because a popular royalty free music creator made it. So lots of creators are using it because they don’t need to pay rights for it.
It’s royalty free music. A bunch of VTubers use it too.
I’m about 99% sure it’s one of Dova-Syndrome’s BGMs. They’re very common.
Learning 自体 the other day made me think of “per se”, and I was wondering, are the Latin expressions like that (or “ad hoc”, etc.) which are ubiquitous in English ever used in Japanese? I don’t remember ever seeing one transliterated in katakana but, of course, I’m not very experienced.
Etc as in et cetera seems fairly well known although I don’t recall seeing it in the wild like that. There’s also etc like Electronic Toll Card, but that’s different.
r for radius (does that count?) is often on road signs for curve warnings.
Not a Latin expression, but writing “xmas” instead of Christmas is pretty common.
I’ve definitely heard it on Nihongo Con Teppei. I think in writing you would be much more likely to see 等(など). I wouldn’t really expect any of the others to be consistently used in Japanese, though.
等 has surely shown up somewhere. 
There was post with a picture showing different pairs of slippers, all in different colours. The OP was asking what colour they should buy. I used my vast knowledge of Japanese (
) to say I liked the yellow ones.
This is how they replied:
黄色も迷いました😁
I can’t seem to understand what they meant? The translation was confusing…
The person who said that is a native speaker?
Yes, this is on Hello Talk, and they are Japanese (or at the very least, that’s what the account says 
)
Maybe just a wording the native I was asking for confirmation doesn’t use themself. But basically I would interpret it as they thought about that but weren’t sure. One meaning of 迷う is to hesitate or waver.
I see, that makes sense, thank you!
I’m not in a position to criticize anyone’s Japanese, but is saying 少子高齢化にともなう人口減少 kinda repetitive? To me 少子高齢化 already implies a 人口減少.
(I read it in this article.)
The population doesn’t have to decrease just because you have a low birthrate and aging population. You could have tons of old immigrants, theoretically.
Also, Isn’t it a bit clearer ? After removing 人口減少 from the sentence of the article it become “while the domestic market is struggling due to the aging of the population…” and I could wonder why, maybe an older population can create market opportunity too ? But with “the domestic market is struggling due to the decline of the population (caused by aging)”, well that’s just make sense.
Right…that makes sense 
迷う can also be translated “to be charmed by” or “smitten” according to jisho.
So I’d guess that’s probably what they meant since they used も to indicate agreeing with you.
I was also unsure about that も and its role in the sentence… So yeah, this also makes sense, thank you!
Recently my friend introduced me to her friend (same age) who wants to learn English. I’ve been messaging her through Line for a few days now, and we’re getting to know one another. At this point it’s mostly in English, but I sometimes say a few things in Japanese. My question is: should I be using polite or casual form?
I wouldn’t overthink it too much. Have they sent any messages in Japanese? One general tip is to just copy what other people do, as long as there isn’t some obvious reason why you shouldn’t (like, they’re your boss, or a super important person).
Another thing is you could just try casual and see how they respond. It’s often the case that Japanese people have never thought about how people who speak other languages learn Japanese, so they may actually assume that polite Japanese is “harder” and learned later even for non-natives, because of the fact that natives go from casual to polite as they learn.
In other words, it’s likely that if you’re a beginner and they know it, they won’t think anything about your choice of politeness. Or if they think polite is harder, they may be mildly impressed with it.