Bokura no Kiseki ~Another Stories~ is a volume featuring three sides stories for Bokura no Kiseki along with a few other works (mostly previously published in Arcana) by the author, Kumeta Natsuo.
The volume was published in July 2018, a couple months after volume 18 of Bokura no Kiseki.
Another story #1 also appeared in the July 2018 issue of Comic ZERO-SUM alongside Bokura no Kiseki ch. 75.