I have recently had a chance to talk with Ziyi Xu and Hui Quan from the University of Tokyo. Both do research on Murakami and they have kindly checked the use of dialogue (or more precisely the lack thereof) in the mainland Chinese and Korean versions of the story "Yesterday."
In the mainland version (published in 2015 by 上海译文出版社) the story was translated by Zhu Jiarong. According to Ziyi Xu, no dialect was used to differentiate Kitaru's speech from Tanimura's. Kitaru is only made to speak in a more colloquial register. Ziyi Xu said that his lines sounded more like "he was from the countryside, rougher."
The Korean version (2014) was translated by Yang Ŏk-Kwan. According to Hui Quan, the translation apparently shows no trace of dialect either in the lyrics in the beginning or in the dialogue.
Thank you, Ziyu Xu and Hui Quan, for your help!
This blog is meant as an open forum where translators of Haruki Murakami can share ideas and discuss solutions to problems encountered in the process of translating his works. It was launched by two translators of Murakami into Norwegian and Polish, Ika Kaminka and Anna Zielinska-Elliott. Some of us have collaborated in the past, and many of us are in touch regularly by e-mail, but the publication of the new novel in 2013 served as a catalyst for the creation of an online translation blog.