These are manga shorts drawn by the illustrator of the novels, Hibiki Reine. They were all printed in the magazine Cobalt, which the novel is serialized in; Before the Festival was also printed in the Marimite Premium Book (ISBN: 4086004550), and the others were printed in the Marimite Illustration Collection (ISBN: 4086007975). All are rather short. As far as we know, no more of these shorts have been done. Related: Maria-sama ga Miteru (https://bato.to/comic/_/comics/maria-sama-ga-miteru-r6020)