underdog's manga / #underwear(1)

6 the story begins with Nasaki ritsu, from the second design department of the company which focus on women clothes & Kasaka seji, the lead desigener of the first design department which focus on making men clothes...and thus begins the clash of the TITANS between both the departments ... clash of differnt approach towards their respective works..But suddenly the company decide to make men underwear & put Kasaka seji in charge which he gladly accepts under one condition that ritsu will be his underwear model..?? What's the underlying meaning of this..?? is he doing this to harrass him or is something else..??