It is intriguing to learn not just about how second languages (L2s) are learned but also about how they can be lost over time after one leaves the environment of exposure to intensive use of the L2. This book addresses the phenomena of language attrition in Japanese adolescent learners of English as a L2 who spent several years in English-speaking countries and then returned to Japan (where the use of English is much more limited). In particular, the author investigated L2 attrition in terms of the functions of the literacy instruction the students received in English while overseas and of the subareas of English affected over time. The overall results revealed that literacy instruction of 4 years in the host country plays an important role in determining whether and to what extent language attrition occurs: Those who had received literacy instruction for 4 years or more not only showed lack of attrition but improved in their lexical knowledge and spontaneous writing and speaking skills even several years after having returned to Japan. Taura claims that three factors are particularly important in accounting for the observed improvement of these returnee students: (a) high enough attainment of L2 proficiency when leaving the L2-dominant environment, which is related to the L2 literacy education received; (b) high motivation on the part of the returnees to maintain their L2 abilities; and (c) favorable educational environment in which to sustain the L2 skills. The cross-sectionally and longitudinally collected data analyzed in this study are rich and detailed. However, it is unfortunate that more detailed information is missing regarding the particular educational environment of the learners upon returning to Japan, the kind of English as a foreign language instruction they received there, and how these may have contributed to enhancing their motivation to either maintain or improve their L2 knowledge and skills further. However, this would probably be asking too much for an already more than 400-page book.