Also known as: 【企画】6月4日リグルリレー, 6月4日リグルリレー, 6月4日はリグルの日
A "Touhou Character Day" based off of a Number Pun, as 6/4 can be read as "Mushi", meaning insect. On this day, artists hold the "Wriggle Relay", drawing Wriggle running a relay race carrying a Relay Baton, and optionally wearing a Gym Uniform.