Hard

It refers to the "strong" nature of diluted alcoholic drinks such as chuhai, green tea highballs, and highballs. When visiting a local Chinese restaurant in Katsushika Ward on the BS-TBS program "Machi Chuka de Nomouze," guest Uchiyama Shinji used the word "katai," and then Tamabukuro Kintaro took to it and started using it, making it popular in bars. It seems that Uchiyama Shinji learned it from TOKIO's Matsuoka, but the origins of the word beyond that are unknown. If anyone knows the origins of the word beyond that, please let me know.