right-handed neutrinos can provide Dirac masses for flavor neutrinos and light flavor neutrinos can be generated if the right-handed neutrinos are very heavy. Furthermore, CP violation in the early universe is able to be induced by the heavy right-handed neutrinos via the Dirac mass terms supplemented by the Higgs scalar. If the heavy right-handed neutrinos come in two families, all of CP-violating phases associated with the Dirac neutrino masses can be converted into the CP-violating Dirac and Majorana phases associated with the light flavor neutrino masses. The model with two extra heavy right-handed neutrinos is called minimal seesaw model [@MinimalSeesaw]. If the seesaw mechanism is the right answer to give tiny neutrino masses, our relation Eq.(\[Eq:M\_nu for 23\]) is also described by more fundamental quantities, namely the Dirac neutrino masses.

In this article, within the framework of the minimal seesaw model, we would like to argue how Dirac neutrino masses are constrained so as to induce maximal CP violation and simultaneously to induce maximal atmospheric neutrino mixing as well [@MassTextureCPEarlier; @mu-tau-CP]. In Sec.\[sec:2\], we introduce six Dirac neutrino masses associated with two extra heavy right-handed neutrinos. Three relations determining three neutrino mixing angles such as Eq.(\[Eq:M\_nu for 23\]) are expressed 