Kirin is a beverage giant in Japan. Aside from alcoholic drinks (Kirin beer in particular), they have large lines of soft drinks as well. This tea comes from their popular Gogo no Kocha (Afternoon Tea) line, and was a "special" version of their regular milk tea.
The back of the bottle (mostly obscured by the label with the translation of the ingredients, as I bought this in the US) said that it was made with Assam tea and milk. I read online that the "special" version here had creamier milk and a more robust tea base. It's been a little while since I had the regular version, so I can't make a comparison.
The tea was very refreshing, with a complex, slightly floral flavor. It wasn't too sweet or too rich, and did taste special. The Assam tea was present, but not strong, which I enjoyed. It definitely worked well as an afternoon tea for that reason. Of course, no matter what time it is, my father likes his tea black and almost over-steeped, so those with tastes like his would not care for this.
The drink certainly wasn't sickeningly sweet by any means. I assume that it was a limited edition release in Japan, but I would certainly drink it again. I will have to try the regular version to see if there are any detectable differences.