It is well-known that children whose native language is Japanese first begin vocalizing potential verbs at about the age of 2 years and continue to utter ungrammatical forms which are not used in adults’ speech as well as correct ones until approximately at the age of 5 years when their acquisition of potential verbs completes, with virtually no erroneous uses observed. Interestingly enough, the process of the acquisition of potential verbs proceeds in a manner parallel with that of causative/inchoative alternation. In this study, based on children’s natural speech data reported in previous research, we argue that the approach put forth in Fuji, Hashimoto, and Murasugi (2008a. “A VP-shell analysis for the undergeneration and the overgeneration in the acquisition of Japanese causatives and potentials.” Nanzan Linguistics 4: 21–41; 2008b. “VP-shell analysis for the acquisition of Japanese potentials.” Nanzan Linguistics: Special Issue 3(2): 65–102) is not empirically valid in that it cannot correctly predict changes in morphological patterns of potential verbs uttered by children along the period of language acquisition. Moreover, in the course of our discussion, it is shown that the acquisition process of the potential morpheme e by children can be identified as that of (in)transitive morpheme e which forms the class of mono-grade vowel-ending verbs.