We use Khovanov-Lauda-Rouquier (KLR) algebras to categorify a crystal isomorphism
between a fundamental crystal and the tensor product of a Kirillov-Reshetikhin crystal and
another fundamental crystal, all in affine type. The nodes of the Kirillov-Reshetikhin
crystal correspond to a family of "trivial" modules. The nodes of the fundamental crystal
correspond to simple modules of the corresponding cyclotomic KLR algebra. The crystal
operators correspond to socle of restriction and behave compatibly with the rule for tensor
product of crystal graphs.