Why aren't some words translated?

If you've watched my fansubs, you might noticed that some words are romanized instead of being translated. Some words, like honorific titles, are left because when translated to English they lose most of their meaning. However, some words are left in due to being names of things like attack, or to preserve the culture. And then there are words that are just left in, because they simply can be.

Oni

Oni (鬼) is the Japanese word for "demon". But let me ask you a question: what do you think of when I say "demon"? Probably some satanic monster that's black and slimy that kills people. I bet that when I say "demon" in English, Nezuko isn't the first thing you think of. Unlike the traditional idea of "demons", oni are often portrayed as humanoid, like in Kimetsu no Yaiba (Demon Slayer) and the Netflix original "My Oni Girl". They don't have to be portrayed as humanoid, because as shown in Kimetsu no Yaiba, some of the demons aren't. But most of them are humanoid.

Onigiri

This one's quite simple! Onigiri (おにぎり) is the Japanese word for "rice balls". I don't feel the need to translate this to English, and judging by the fact that "onigiri" triggers Google's knowledge panel but "rice balls" doesn't, most people probably already know what it means. (And if you're one of the people who don't, well that's why you're here!)

Shōnen and Shōjo

A shōnen (少年) is a young boy, and a shōjo (少女) is a young girl. That may seem simple enough, but they aren't just used to describe people. In Boku no Hero Akademia, All Might commonly refers to the students as "Lastname-shōnen" - so they can also be used as keishō. In addition, shōnen and shōjo are also used to refer to demographics of anime and manga (and other things too) - with shōnen being aimed at boys in the age range of 12 to 17, and shōjo being aimed at girls in the same age range.

Keishō

Keishō (敬称) is the Japanese word for honorific titles. Not only do I leave keishō themselves untranslated, along with words like "onii-san", but I leave the word that refers to them (keishō) untranslated as well.

Keigo

Keigo (敬語) is the Japanese word for honorific speech. Honorific speech is NOT the same as honorific titles! Honorific speech is the idea of speaking respectfully. However, it's way more integrated into Japanese culture than the concept of "speaking respectfully" - a translation that is accurate, yet still doesn't capture the full meaning.

敬語をしてください！
Please usekeigo!

I honestly think that both keigo and keishō deserve to be left untranslated.

Anime and Manga

These words are interesting. Anime (アニメ) is the Japanese word for cartoons, and manga (漫画) is the Japanese words for comic books. They don't have to be Japanese cartoons or Japanese comic books - refferring to Marvel as manga is actually correct (in Japanese, at least). Most people when watching anime know that if the characters say anime, they're talking about cartoons in general. Honestly, there's not really a need to translate anime and manga when they're so widely known.

Konbini

Konbini (コンビニ) is the Japanese abbreviation for a convinience store. And that's it. It's literally just that, but one thing writing it as "konbini" does is save space and decrease the required reading speed. "Convinience store" has 17 characters, including spaces. "Konbini" only has 7. It could also be written as "conbini", but that looks off to me, and you'll probably never see me write it like this. I prefer the actual spelling of "konbini".