Washio Sumi wa Yuusha de Aru Gaiden: Yuusha Koushinkyoku

Chapters 1-6: Washio Sumi wa Yuusha de Aru Gaiden: Yuusha Koushinkyoku
In this humorous, slice-of-life spin-off of Washio Sumi is a Hero, Sumi, Sonoko, and Gin set out on an adventure to return a lost puppy to its owner.
Chapters 7-9: Kaettekita Washio Sumi wa Yuusha Radio
Chapters 10-11: Yuusha GP
"Hero Grand Prix" is a cross-over that includes the characters from Yuki Yuna is a Hero, Washio Sumi is a Hero, Nogi Wakaba is a Hero, and Shiratori Utano is a Hero.