The Wrong Way to Use Healing Magic Volume 2: Light Novel

Usato gets his first taste of battle after surviving the hellish training of the rescue team! Making the most of his newfound abilites, Usato aids the injured and heals the wounded, but danger lies just around the corner for his friends, Suzune and Kazuki!
The two heroes find themselves face to face with the Demon Lord army's black knight, a foe equipped with a terrifying, ominous suit of dark armor that's seemingly impenetrable to any and all attacks. When their efforts amount to nothing, Suzune and Kazuki are left with their backs against the wall--the black knight's blade getting ever closer.
To save his friends, Usato will have to make healing magic his weapon and use it the "wrong" way to topple this ostensibly invincible foe.