For the sake of another, I fight

Scattered across the peaceful city of Kawado Higashi are "Guilt Seeds" that cause people's desires to run wild, turning them into dangerous monsters.

To prevent the inevitable disaster that would occur if left unchecked, Ichika Itakano charges Haruno Aikawa with the collection of these seeds. With her newly acquired ExS-Device, Haruno is able to transform into ExS-TIA Ignis and search for the Guilt Seeds.

At the same time, another ExS-TIA emerges from the darkness of night. Toka Sugawara, who attends the same school as Haruno, a.k.a ExS-TIA Luna. She too hunts for the Guilt Seeds while battling against monsters.

But what could be the ordinarily modest and quiet Toka's reasons for fighting as ExS-TIA Luna...?

[From MangaGamer]