Why do Yuko's poems always end in 'Mogami River'? Several times during the anime, Yūko Aioi ends her short haikus with 'Mogami River'.

I've read on the Wikipedia page for Mogami River that Matsuo Bashō used it in at least one of his poems, but I can't much written about it, so it seems to me to be not a well-known feature of his poems.

Is this the correct reason for the inclusion of the line, or is there an alternative reason?



(I couldn't find an image with subtitles, so hopefully this is a correct example)
According to this academic site, while it is not a kigo (season word), the mogami river is well known in Japanese haiku.

I imagine Yuuko has trouble thinking of an entire 5-7-5 poem, and so she just reuses this famous line for that reason.