Yuuki Yuuna is a Hero

is a Japanese manga series written by Project 2H and illustrated by Touko Kanno. The manga was serialized in the Dengeki G's Comic magazine and published in Japan by ASCII Media Works under the Dengeki Comics NEXT imprint from November 2014.

Synopsis
In her everyday life, Yuuna Yuuki is a hero. As proof, she is in her middle school's Hero Club, where she does her best to help others and bring a smile to everyone's face.

But Yuuna, always up to any task, is about to become an even bigger hero. Mysterious destructive forces called Vertexes begin threatening the world she loves, and the Hero Club is called upon by a strange phone app to save it. Along with her best friend Mimori Tougou, as well as sisters Fuu and Itsuki Inubouzaki, they must transform into magical girls in order to battle the Vertexes.

In between studying and putting on shows for kids, Yuuna and the Hero Club must fight for the very existence of their world and face the harsh truths behind their own powers, all the while discovering what it truly means to be a hero.

(Source: MAL Rewrite)

Yuuki Yuuna wa Yuusha de Aru: Washio Sumi no Shou
The series was written by Takahiro and illustrated by Nitaka Ichifuji. It was serialised published under the Dengeki Comics NEXT imprint from November 2017.

Yuuki Yuuna wa Yuushabu Shozoku
A Chibi Spin-Off of the Yuuki Yuuna is a Hero series. It was written by Takahiro and illustrated by Kotamaru. It was serialised in Dengeki G's Magazine and released under the Dengeki Comics EX imprint from December 2014.

Washio Sumi wa Yuusha de Aru
In the year 298 from the era of the gods, elementary school girls Sumi Washio, Sonoko Nogi, and Gin Minowa are tasked with an important mission. They are to become heroes and fight Vertex, a mysterious enemy that is attacking Shinju-sama, the god tree that protects Shikoku, the only area in the world that is still habitable. What they don't know, is that this fight will cost them more than they could have ever imagined.

The series was written by Takahiro and illustrated by moo*. It was serialised in Dengeki G's Comic and released under the Dengeki Comics NEXT imprint in December 2014. It was discontinued after the first volume.

Washio Sumi wa Yuusha de Aru Gaiden: Koushinkyoku
A spin-off of Washio Sumi is a Hero with the story by Takahiro and art by Kotamaru. It was released under the Dengeki Comics EX imprint in April 2017.

Nogi Wakaba wa Yuusha de Aru
The story of Nogi Wakaba is a Hero takes place 300 years in the past, in the first days of the Divine Era. There are six main characters who form the very first Hero Team: Nogi Wakaba, Kamisato Hinata, Takashima Yuna, Gun Chikage, Doi Tamako and Iyoshima Anzu.

The series is written by Aoi Akashiro and illustrated by Daisuke Takino. It was serialised in Dengeki G's Comic and released under the Dengeki Comics NEXT imprint from November 2016.