The study anchors on the Linguistic research tradition of Error Analysis (EA), focused on the grammatical errors, specifically on "verb tenses" manifested in the sentences of Japanese ESL learners. The entire respondent population was drawn from the pool of registered learners in 2017 at the Clark Institute of the Philippines Foundation, Inc., Angeles City, Pampanga. The researcher classified the learner errors using Corder's Taxonomy of Errors, with a tripartite error typology that includes "selection", "omission", and "addition". Moreover, the frequency and types of errors were statistically correlated to the learners' profile variables that include age, sex, years of exposure to English, educational level, and hours spent per day on different mass media in English. Descriptive and correlational research designs were employed, with the use of a researcher-developed data-gathering instrument. The instrument includes two parts, i.e. a questionnaire for profiling the respondents and a writing activity. Aside from the researcher's assessment of the written discourses, professional assistance was sought from three (3) ELT experts, namely: the Training Director of the research locale's academic team, an IELTS/TOEFL trainer, and a TESOL trainer who co-evaluated the respondents' written compositions using the Cambridge Grammar of English Language. As to the learners' profile, majority of them are female and register to ages ranging from 11 to 30 years old. The learners' highest educational attainment ranges from Elementary School graduate to Post-Graduate Studies. All learners spend from one to more than three hours accessing a variety of mass media in English. From the error analysis of the learners' written discourse, they accounted for errors in certain types of verb tenses. Moreover, the errors are distributed in all the three types of errors in Corder's taxonomy, with most of their errors registered under "selection", followed by the frequency of their errors in "omission". The learners have few traces of errors under "addition". On the merits and essentials drawn from the study's findings and conclusions, several recommendations are offered. Also, learners are advised to spend more time on the internet to reduce their omission errors. Likewise, teachers have to exploit the use of mass media in the instructional design, taking advantage of the learners' high frequency of access to these social amenities.