Kieli, Vol. 2 (light novel‪)‬

As the holidays wind down, Kieli continues her "research trip" with her
companions - Harvey, a near-immortal soldier known as an Undying, and
the Corporal, a soldier's spirit possessing an old radio. Their fates
irrevocably intertwined by a bloody war waged eighty years ago, Harvey
has promised to help the Corporal pass on by returning him to his final
resting place...even with Kieli tagging along. But when saying their last
good-byes to the Corporal goes awry, and they are attacked by Church
soldiers after Undying hearts, Harvey is convinced that it would be
best for Kieli to go home. But is it really Kieli that needs saving...or
is Harvey sacrificing his last hope for salvation?