Cleaning in Progress

Found this sign at Narai Station. At first glance it's an ordinary sign letting one know cleaning is in progress so I could have left without capturing it, but please look closely at the picture: the person depicted looks to be proud somehow. I've never seen this sort of picture in similar signs before.

When me and my father arrived at the station it started to rain. Neither of us brought an umbrella but the staff in the station kindly lent us ones.