One important clue to why IGJ starts out in a
different, much more positive mood than Horn was in at
the end of OBW can be found, naturally enough, in
Chapter 1 of IGJ: the encounter with Cugino. It's not
only that Cugino's friendly helpfulness restores some
of Horn's confidence in the potentiality for human
goodness, a small demonstration that Horn
psychologically multiplies; more, Cugino's crafting of
a staff for Horn symbolises the possibility of the
liberation of humanity (the tree) from the oppression
of the inhumi (the creeper). I suspect that this
unobtrusive scene can help illuminate the secret of
the inhumi; it certainly lifts Horn's spirits considerably.