The sequence /zi/ does not occur in the Japanese language, and in loanwords from English, it is adapted as /dʑi/, e.g., English busy - Japanese /bi.dʑi/. While similar sequences of alveolar obstruent plus high vowel, such as /ti/ or /tɯ/, also used to be avoided in Japanese, they are occurring in recent loanwords. Such formerly impossible sound sequences are likely to have emerged because current Japanese speakers have more contact with English than previous generations: extended exposure to English with its less restrictive phonotactics leads younger speakers to acquire less strong restrictions against the sequences in question in their Japanese. In the present study, we tested whether Japanese listeners are sensitive to the difference between [zi]-[dʑi] in an online AX discrimination task. Our participants ranged in age from 18 to 65. We hypothesized that younger listeners would be better at discriminating [zi]-[dʑi] in non-words as they had more exposure to English, which allows /zi/. Our study could not confirm this hypothesis. Instead, we found large individual variation in performance, and a good discriminability in general, which leads us to expect that the occurrence of /zi/ in Japanese loanwords is imminent.