This book contains new research essays of linguistic interface studies in or related to East Asian languages. Written by 14 colleagues or former students of Yoshihisa Kitagawa, it is also a book paying tribute to his decades of scholarships on linguistic interface studies. The chapters therein range from interface studies in syntax and other linguistic areas such as morphology, phonology, semantics, pragmatics, language acquisition, language evolution, and language faculty science. The languages under discussion are mainly East Asian languages such as Chinese, Japanese, and Korean, but also include Jordanian Arabic and Spanish, under comparative studies with respect to East Asian languages.