@tomoki so welcome to the Chinese (language) world 👍
you can ask me about Chinese, if needed. i am a native Chinese (mandarin and Xiang dialect) speaker.
and there are many others who using Japanese mostly but learning Chinese, in this Fediverse. if you use Matrix.org as a chat tool, you can find a group for Chinese language learners. the online chat room address is #learn-chinese:matrix.org
hope you all well!