Emotion plays important roles in learning, memory, and other cognitive processes; it does so not only in the form of "macro-level emotion" (e.g., salient affective states and self-reportable motivational currents) but also in the form of "micro-level emotion" (e.g., subtle feelings and linguistic attributes that are usually processed subconsciously without special attention). According to the Emotion-Involved Processing Hypothesis (EIPH), processing that draws attention to emotional aspects (EmInvProc+) is postulated as a deeper version of semantic processing which has cognitive advantage to facilitate linguistic processing and retention more than non-emotional semantic processing (EmInvProc-). This study empirically investigated whether the EIPH can be experimentally corroborated for learners of a distant foreign language (viz., Japanese learners of English). In the experiment, participants processed visually presented English words that were either positively or negatively valenced under different conditions, followed by the test session in which they engaged in memory tests. Two processing modes were compared (EmInvProc+ vs. EmInvProc-). The dependent variables were correct recall frequency, correct recognition frequency, and correct recognition reaction time. It was revealed that EmInvProc+ was more cognitively facilitatory in making stronger foreign language lexical memory traces than EmInvProc- for all the measures employed in the experiment, regarding both accuracy (correct response frequency) and fluency (correct response reaction time). Therefore, it is implied that EmInvProc+ can be regarded as a sui generis deeper level of processing that is qualitatively distinguishable from mere semantic processing, supporting the Emotion-Involved Processing Hypothesis.