Mangaka did some special Kyuu-chan content on Twitter for Christmas:
https://twitter.com/nitorisasami/status/1209397631937478657
And for Happy New Year:
https://twitter.com/nitorisasami/status/1211930888746831877
https://twitter.com/nitorisasami/status/1212026042392690690
She also did a special manga to promote manga Vol 5's release, available in both print and ebook format.
https://twitter.com/twi_yon/status/1216118851479461888