Leith Casel-Schutz has been heavily involved in Filipino language (Tagalog) instruction to non-Filipinos for close to five decades, beginning with the training of former US Peace Corps volunteers in the Philippines. After conducting comparative research on Filipino and Japanese at Tsukuba University as a Mombusho scholar, she taught Filipino language and culture to Japanese university students as a visiting assistant professor at the Tokyo University of Foreign Studies (TUFS).  She has also taught Filipino intensively to Japanese corporate employees, civil servants, diplomats, and police officers, and has written several Filipino language conversation books along the way.  More recently, she co-authored a comprehensive TUFS-published Filipino language textbook which is now the bestselling source on Filipino language learning and teaching in Japan.   At present, she and her colleagues are working on a Japanese-Filipino dictionary which they hope to publish later in 2024.