Numerous studies have found "subject gap preference" in relative clauses and cleft constructions in English, French, and other languages. In contrast, previous studies have reported "object gap preference" in cleft constructions in Japanese. However, the effect of integrating a filler and its gap may be influenced by the effect of transitional probabilities, so previous studies confounded these two factors. This study explores processing asymmetries in Japanese cleft constructions by conducting an event-related brain potential experiment by controlling transitional probabilities. The results demonstrate that the subject gap preference in Japanese is well aligned with that observed in other languages, suggesting that subject gap preference is a universal aspect of language comprehension.