Found in the old Zakon back area.
The ramen restaurant Daruma-no-Me Akihabara is currently offering a 10 yen sale on doubedama (usually 100 yen).
This is the second 10 yen sale since last November, this time from January 21 to 23.
There are two types of tobidama: white (normal noodles) and red (noodles with hot pepper paste), both of which can be ordered without limitation for 10 yen per ball.