hi anon! this IS actually a really hard question OSHDKDND so i brought it up to my translator friends and a lot of us just kinda agreed that it's... based on vibes LOL i know that's not all that helpful but hmm... we also talked about how a lot of it based on the media you consume and the people you talk to, like how i don't know many people who speak with a southern american accent so it's difficult for me to write koharu. in a way it's also kinda based off of like... tropes(?) of certain characters and how they usually speak if that makes sense?? like oh ryui has kind of a delinquent vibe and in japanese he speaks roughly and rudely so i elect to translate that into him cursing a lot and using more casual words in english

mmmm i feel like it would be easier for me to explain by explaining my personal choices for each 18trip character one by one rather than talking about how i do things in general AIAJIDND so if you're curious about any character in general you could let me know anon! i know this probably wasn't all that helpful 😭 but thank you for the question anyway !!