This study investigated the degree to which Japanese learners of English accurately perceive English fricatives over time and the extent to which fricatives were misidentified. To train and measure perception skills, an online high-variability phonetic training program was used in an English as a Foreign Language (EFL) class in Japan for eight weeks. The results indicated that learners' perception of some of the fricatives improved over time, while others remained difficult to distinguish from other fricatives. Implications for EFL pronunciation instruction are considered. [For the complete volume, "Intelligent CALL, Granular Systems and Learner Data: Short Papers from EUROCALL 2022 (30th, Reykjavik, Iceland, August 17-19, 2022)," see ED624779.]