Hello? Hi! Welcome to Misono's phone for the week of February 21st to February 27th. As always it takes phone calls/voice mails/e-mails/texts and if you can leave the date/time/method of contact in the subject, she'll get back to you ASAP. It'll probably be long winded or incoherent (or both) but it will be (somewhat) in regards to your question/request/happy news/scolding.
Current wallpaper:
Misono tends to use the modern 'standard' Japanse (that is, the Tokyo dialect) when she speaks. It's standard for a reason. She MOSTLY speaks English almost all of the time. If she's just waking up she'll lapse into Japanese or if she's talking to herself she might but mostly it's English all the time. Unless she knows that somebody speaks Japanese.
With Aiba in Come Again she uses mainly English--it's work and there are probably people around and it is rude to exclude them. And while she's spoken almost nothing but English for the last fifty-odd years (and has heard it almost exclusively for the last seventy), upstairs or alone or just out and about I imagine she uses Japanese probably about as much as she'd use English. She'll revert to the really old stuff she spoke when she was younger for one of two reasons: She wants it to remain between the two of them (and suspects that whoever else is in the room MIGHT be able to understand modern Japanese standard) or else she is very upset and has reverted back to it unconsciously. Sort of like baby-talk, only not quite.
With Ryo, Misono uses kansai-ben. It's probably a hundred years out of date slang-wise but she'll catch on quickly enough (even though it means she'll talk like a dude). In Come Again she'll stick to English--again, it's work!--but there is a good chance she'll use Japanese with him any where else. Even more so than she would with Aiba because Ryo's English isn't that great and he's still getting used to hearing it all over the place (it took Misono a good twenty years to get over THAT shock). Plus. RYO IS FROM OSAKA. They're practically related. AND it's her 'home' accent.
She doesn't speak to Ohno but the same would hold: She'll use English most of the time if there are other people around but she'll use Japanese if it's just the two of them. Or if she wants to keep what she's saying a little more secret. She doesn't understand the Okinawan dialect (if he even uses that--he IS from UNDER the water there). Nevermind, he mumbles. :D
With Shun she uses, again, English and the Tokyo Japanese. If he's using Japanese, that's where she'll go and if he's using English, that's what she'll use. And again, she's been using English for at least fifty years with both fluency and exclusvity. She's kind of used to it. She'll follow his lead.
Tego! Whom she has not yet met. His English isn't great so she'll probably stick to Japanese unless she feels their location requires her to use English with him.
If any of our Japanese speakers would like to correct my take on this as regards you, let me know.