This paper analyzes the use of and the perception on the Japanese loan words in four different age groups including teens, 20s to 30s, 40s to 50s, and 60s to 70s. The exposure to the remaining Japanese loans is high to the age groups of 40s to 50s, and 60s to 70s while it is low in the teens. All age groups are frequently exposed to the food-related loan words. It is also observed that the remaining loan words undergo semantic changes: expansion or reduction of meaning. Some loan words adopt different meaning from their original meaning in Japanese. Some loan words are deeply rooted into the language life of the Korean language users even though their counterparts exist in Korean, and they are naturalized as Korean words and listed in "Standard Korean Dictionary(표준국어대사전)." It is assumed that the loan words may well be fully accepted into Korean language when they are in frequent use and when the people are not aware of their origin. On the other hand, the loan words may become obsolete and disappear when they are frequently replaced by Korean native words because they are recognized as loan words by Korean language users.