This document reports on a study of errors made by Japanese university students in their English writing that are influenced by their first language of Japanese. The researchers built a "house-made learner's corpus" of over 178,000 words by collecting writing samples from forums and blogs on Moodle platforms at three universities in Japan. They analyzed the samples and found common error types such as incorrectly using the topic rather than the subject of the sentence, missing or misusing pronouns, and confusing parts of speech and predicate-argument structures. These errors reflected the influence of Japanese syntactic structures on the students' developing English interlanguage. The researchers suggest exercises to improve learner awareness of these cross-linguistic differences as a way to address these common