This is draft beer topped with something frozen. It looks like ice cream, but it is not sweet or normal froth.
Actually, it is icy froth which is also made of beer.

This icy froth is the best way to keep beer in nice flavor and very cold temperature.

Bars / restaurants have to prepare the special beer server for frozen beer. So, frozen beer is still uncommon. It is getting popular though.
Drinking frozen beer is a good beer experience. Would you like to drink it?
This frozen draft beer is made by KIRIN.
Example shop list
* Find some branches which are named キリンシティ…新宿… on the website above. These branches are located near Shinjuku 新宿 Station of Tokyo 東京, and easy access.