Following an initiative to include Japanese and Korean into the Altaic macro-family by Philipp von Siebold (1832) and a systematic linguistics-oriented investigation in the late 19th and the early 20th centuries by Gustav John Ramstedt (1952, 1957, 1966), the question whether the Altaic macro-family is a genealogical unity (Miller 1971; Menges 1984; Robbeets 2005) or just a group of languages that share similar typology (Janhunen 2007; Vovin 2009; Tranter 2012) is still disputed. On the other hand, the existence of a common ancestor between Japanese and Korean has recently gained more supporting linguistic evidence (Whitman 1985; Francis-Ratte 2016), although a large group of proposed Proto-Japanese-Korean lexical items are not completely unproblematic when applying strict criteria of regular sound correspondences and semantic field (e.g., Janhunen 1999: 10; Vovin 2010). Instead of directly revisiting their origin, the present study devotes attention to typological features that distinguish Japonic and Koreanic from the other Altaic languages both on the synchronic and diachronic levels by taking into account also historical languages. As a main method, a quantitative-typological approach also allows comparison of various languages spoken in Northeast Asia without any assumption about their common origin, unlike in etymological studies (cf. Unger 2013; Francis-Ratte 2016).