Yuki Yuna is a Hero:The Washio Sumi Chapter/Hero Cahpter

Yuna and her Hero Club friends are transported to a strange forest to become real heroes and fight a mysterious enemy known as the Vertex.

The Hero Club deals with the aftermath of their first Vertex battle; Fu reveals the explanation for their transformation into superheroes.

After a brief break in the real world, the club must battle Vertex Capricorn. It is a rough fight until help arrives from the Taisha organisation.

The heroic friends still have school responsibilities, including Itsuki's upcoming singing test, so the club helps her out with a karaoke rehearsal.

To fight the seven remaining Vertex, each girl calls upon her individual Mankai power, risking the loss of one or more physical functions.

Thinking their battle days are over, Hero Club learns the price of using their Mankai powers, including loss of vision, hearing, taste and speech.