Shion decides that Coco is being too formal with her, and tries to bring their relationship closer by teaching Coco a thing or two about Japanese. This may be the origin of all of the "Shion yo!" comments that have been appearing in her streams as of late.
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Translator Notes
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I took some liberties with the translation in an attempt to use similar concepts that apply to English. The exception mainly being the particle 'yo', which doesn't really have an equivalent in English. Take it at face value here that adding it to the end of a sentence can make it sound more casual, but obviously Coco took that to the extreme by interlacing it everywhere throughout her sentences.
I explicitly added all the subsequent uses of 'yo', as in most cases, either Coco adds it deliberately, or she reacts when Shion uses it.
3:30 - Shion is either being tongue in cheek here, or is deliberately misleading Coco. There are many situations in Japan where you would be expected to speak formally, e.g. speaking to a senior. She goes back on her words when Coco deliberately misinterprets how to behave, and the chat certainly calls her out on this as well.
6:00 - "Paisen" is a cheeky way of saying "Senpai", which is used here to address her senior. Throwing away the honorifics is a way to show that they are more intimate.
11:33 - Shion mentions an accent (訛り namari), but Coco starts talking about lead balls (鉛玉 namari dama).
13:27 - As far as I'm aware, Coco just trails off into gibberish here.
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Sources
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Original stream: Polite language is forbidden after the casual chat classroom! (Feb 7 2020)
• 【#紫龍組】ため口教室の後は敬語禁止！試され...
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Murasaki Shion: / @murasakishion
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