What's difference between ing and in'?

It's just a pronunciation difference. It can be a result of speaking quickly and casually, or it can be a dialect feature. The rough character is probably supposed to sound rural or uneducated (although the latter isn't fair).

To add to what everyone else has said here, since I've played P5R, I can confirm that the translation makes that choice for Ryuji to indicate that he's less educated/refined and more informal/coarse -- as you've identified, he's "rough." Writing his dialect that way quickly and easily establishes that aspect of his character for English speakers. We understand it from the first time he speaks. :)

in' is informal and is in some dialects

*in'* is a way to represent in writing the extremely common pronunciation of -ing in informal speech: /ɪn/ instead of /ɪŋ/. Sometimes this is called "dropping the g" even though I a more accurate understanding, both pronunciations have two sounds (one vowel and one consonant) and nothing is dropped.

“in’” indicates that the speaker is speaking more casually and is perhaps slightly unrefined i.e. 1) He’s singing a song vs 2) He’s singin’ a song

"ing" is the grammatically correct way to end a gerund in English. "in'" is a way of transcribing an informal pronunciation of the word in some dialects. For example: Writing and reading => a character speaking in formal English Writin' and readin'=> a character speaking informally or in a regional dialect

There’s no difference in meaning, in’ just represents more closely how some people commonly speak. The dialects where this sound change is most common are often associated in media with either being less educated and/or lower class. I would assume there is some comparable accent association in Japanese that the translation is trying to convey. Presumably they have certain characters speaking this way to represent that they are either tough, street smart urbanites or that they are rural bumpkins.

The informality of "'in" is very common among my friend group. I'll often say "whatcha doin?" Or "howsit goin?" When greeting people I'm familiar with, but I would never say or write it in a formal speech setting. The rules of formality vary place to place. I would also greet my boss this way in my industry and region, but I know this would be seen as unprofessional in other industries or regions

"-ing" is grammatically correct. "-in'" is how people often sound when they talk. Sometimes you'll see it written to reflect that. It's kinda like shortening "kind of" to "kinda". Just sayin.

Some English speakers drop the G sound when saying -ing words. It's the exact same word though. It's just spelling it the way they talk instead of using the proper spelling

When it was on TV in the UK, it was shown at 10.15pm on weekdays Staying up past midnight 4 nights a week is a commitment for people who have to work the next day

Ing - proper pronunciation. Long “I” vowel, “eeng.” In’ - colloquial, short “I” vowel, like in “tin.”

If I understand your question you're asking why one word is spelled 'saying' and the same word is sometimes spelled 'sayin' ? It's the same word just with the apostrophe substituting the letter g. It could be called colloquial or slang or an accent. I would stick to 'saying'.

It's a stylistic choice meant to show either a dialect or informal speech where pronunciation is less precise. This style is slightly controversial. Obviously not a big deal, but some people really dislike it. The issue people have with it is that even if I am technically pronouncing it "in'", what I'm saying is the same thing that is normally spelled "ing." The intentional misspelling really just makes the character seem unintelligent or unsophisticated, and sometimes becomes a substitute for good writing.

Just want to add that it's not a binary choice here, there's a range in-between, where it's pronounced more like -ing but the word becomes unvoiced towards the end. Pure, no "g sound" at all -in' (He was runnin', I was fishin') sounds, to me anyway, very rural and lower socioeconomic class. The in-between unvoiced "ng" is by far the most common. Fully voiced "ing" is usually for academia or venues where the speaker is making an effort to speak perfectly.

It's an accent thing. Some under-pronounce the 'g' sound so it just sounds like 'run in', 'swim in', etc. Meaning is identical. It may also be done to better flow the end of the word into the beginning sound of the next word, but that's arbitrary. No rules about when to do that. You can default to 'ing' for everything.

Nothin'

Oh, this is Ryuji, right? You're correct: the game developers chose to drop the "g" to make him sound more rough. Thinkin', f*ckin', anythin' etc. There's no functional difference between with the "g" or without. It's purely to show his rough personality.

Ryuji is a delinquent character, so he often uses informal speech. When he says, "What's bonkin'?", he really means "What's bonking", but the apostrophe is meant to convey delinquency and informality as he speaks. It's simply a way to speak in a fun way or to be friendly.

They're the same word, same meaning, but the apostrophe replaces the g to show that the g is not being pronounced. It's informal to not pronounce the g, and generally you wouldn't write it without the g except very informal situations like text messages (but then you'd drop the apostrophe too) unless you were depicting the way a character speaks in a book or video game.

People who talk right say "saying" And then there's us tharr Suth'ners who say sayin'

I usually “drop the g” myself in speaking, but never in writing, unless I was writing dialogue and wanted the character to sound like that.

It’s a pronunciation difference. “ing” corresponds to the IPA sound /iːŋ/, whereas “in’” corresponds to /ɪn/ or /iːn/. Usually it’s only used in quotes to denote the accent of the speaker or the formality of a conversation, with “ing” being more formal and generally associated with more academic accents like Received Pronunciation and General American, whereas “in’” can be perceived as someone talking less formally, faster, or with some specific accents like Appalachian or Yorkshire.

- -ing Usually a writing element that some authors use to indicate a character is refined, educated, high-class, prim, formal, proper, and/or a cold-shoulder class snob. - -in' Usually a writing element that some authors use to indicate a character has a informal, rural/farmland accent, "hillybilly" or "boonies" accent, cowboy/Wild West accent, welcoming/nice disposition, marginally educated, simple life, and/or low class, maybe a criminal background, etc.

It’s a dialectal difference.