This is the 3107th most frequent Japanese word.
余談
"余談" means a digression or side comment unrelated to the main topic.
Here, '余談' refers to 'a side remark or digression' in switching the topic from something formal to informal.
今日は仕事の話は終えて、少し余談に移りましょう。
Today, let's finish the work talk and move on to a little side conversation.
In this context, '余談' is used to introduce an additional, non-essential piece of information, akin to 'by the way'.
余談ですが、彼は最近新しい趣味を始めたそうです。
By the way, he seems to have started a new hobby recently.
Here, '余談' signifies 'tangents or anecdotal comments', which are engaging departures from the main topic in a narrative.