There's a strangely translated name for you: "University Potato".
Traditionally enjoyed by students in autumn, these easy to make, candied sweet potato bites are known as Daigaku Imo in Japan. A traditional Japanese treat made from sweet potato pieces coated in a flavourful blend of sesame oil, sugar, soy sauce and mild vinegar they make a great sweet-savoury snack as the nights draw in.
I'd have snapped a photo of them in their little bag, if we didn't devour them within a couple of minutes whilst hiding from the rain underneath the train tracks.