Earlier quoted context omitted.
why are you adding japanese honorifics when the rest of your post is in english?
In non-English texts it is not unusual to see English honorifics like Sir, Lord, Lady, Duke etc. or even Dr., Mr., Mrs. Similarly, in English texts it is not unusual to see foreign honorifics besides the actual names. It is quite frequent for someone who otherwise does not speak another language to address foreigners as they would be addressed in their own language in formal situations where politeness is expected, e…
I've also heard that it's still common to address one's peers with -kun in parliament.
In GP's case it sounds rather quaint, but also endearing (like referring to a neighbor or a long lost schoolmate in the third person)
Pedantry: Takaichi is her father's surname. (I had to look that up, tbh)