fiction orphan white hair in 19th Japan and WW1

first-person fiction 19-20th century Japan
read 10-12 years ago
for adolescents
read in german but probably english in original
rather short title

white haired orphan w/ strange abilities
from a caucasian family but growing up in japan
parents died tragically
friends with young emperor
japan society plots
world war 1 as healer always at front and never gets shot

Please help me out