  In 2002, Terao showed that every reflection multi-arrangement of a real
reflection group with constant multiplicity is free by providing a basis of the
module of derivations. We first generalize Terao's result to multi-arrangements
stemming from well-generated unitary reflection groups, where the multiplicity
of a hyperplane depends on the order of its stabilizer. Here the exponents
depend on the exponents of the dual reflection representation. We then extend
our results further to all imprimitive irreducible unitary reflection groups.
In this case the exponents turn out to depend on the exponents of a certain
Galois twist of the dual reflection representation that comes from a
Beynon-Lusztig type semi-palindromicity of the fake degrees.
