These two have the Railroad Engineer insignia, but they also have cherry
blossom branches below, just like the
Imperial Guard insignia. This is a branch of
the Imperial Guard.
Railroad Engineer Insignia
Very similar and related to the Railroad Defense insignia is the Railroad Engineer
insignia. While the former has a cross section of the rail and two crossed rifles, the
latter has the rail and two crossed axes. Both troops were stationed in Manchuria
and were responsible for the extensive railway there.

Here are some examples of the Railroad Engineer insignia.
See my
Train Engine page, too, since many of those cups have the Railroad Engineer
insignia.
Inscribed 'Railroad 2nd [Regiment] Commemorative'.
Kutani cup with Railroad Engineer badge
Inscribed 'Railroad 1st Regiment
Commemorative, Tanaka'.
Rail Defense 1st Regiment
Hand-painted train engine cup . Inscribed
'Railroad 2nd Regiment, Discharge
Commemorative'.