We introduce a neutrino mass model for leptogenesis where three right-handed Majorana neutrinos are involved, and the minimal-extended seesaw mechanism including an additional singlet field produces four light neutrinos. In the model, the type of mass ordering and heavy Majorana scales are determined by inputting the simplest orthogonal matrix into the Casas-Ibarra representation of seesaw. The CP asymmetry produced from the decays of heavy neutrinos and the dilution mass are predicted in terms of the mass and mixing elements of the fourth neutrino, which is possible under the condition that the four-neutrino mixing is unitary. Consequently, the existence of a light sterile neutrino is required to explain the high-energy lepton asymmetry in light of phenomenological measurements. Although there are several free parameters attributable to an additional neutrino, the model can be in part constrained by low-energy experiments such as sterile neutrino searches and neutrinoless double-beta decays, as well as the observed baryon asymmetry in universe.