"Tatsumaki's Day Off" (タツマキの休日, Tatsumaki No Kyuujitsu) is an extra chapter included with Volume 10.
Gigakigan awakens in an unknown city and is prepared to wreak havoc, but is quickly defeated by Tatsumaki. Tatsumaki then complains to a staff member about the Hero Association's over-reliance on her. The following day, Tatsumaki receives no duty calls and is told by the Hero Association staff that she has the day off. However, much to Tatsumaki's displeasure, this lack of work leaves her bored. She decides to go after monsters anyway and uses news coverage as her informant. This leads her to Z-City, but the monsters she wished to go after were already killed by Saitama. After this incident occurs multiple times, Tatsumaki becomes infuriated and rushes to the next alert location as fast as possible and completely decimates Hotdog when she reaches it. Finally feeling relieved, she flies off.