Who is the uniformed guy in this Owarimonogatari end card?
This is a reference to a college-aged Kosaku Shima, the titular character of Kenshi Hirokane's Student Kosaku Shima series.

College students in the Showa era wore uniforms like this. This uniform and emblem is specific to Waseda University, Kosaku Shima's alma mater. 




The public Twitter for the series even made a tweet about the end card: https://twitter.com/shimakosaku1966/status/675702573433663488