|Spoiler Alert: This page contains spoilers. Read at your own risk.|
The Extra (数字落ち) are members of Families who lost their number in their Family name.
The reasons for stripping off their number could be from causes such as: the crime of treason, the crime of failure to perform an important duty, or ‘incompetence’.
Just like discrimination against Course 2 students at National Magic University Affiliated High Schools, this has not been exterminated, and is still being practiced. It has grown even worse, and is in the process of becoming a severe problem; this invisible glass ceiling of discrimination against 'Extras' still persists.
In Shiba Tatsuya’s generation, not many are aware that their family name indicates that they were descended from an 'Extra', because their parents hid it from them. The reason being that deeply rooted prejudice would cause them to be regarded as a "failure" and "defective merchandise", which would be inserted into their consciousness as magicians.
- Known Members:
- Ichihara Suzune (市原 鈴音)
- Once the Ichihana (一花) Family, the name was changed to Ichihara (市原).  The Ichihana being from the First Institute, gained the magic to disable opponents and thus interfere with them by manipulating their nerves. This resulted in the Number "One" being dropped form their name.  The magic in question that can directly interfere with the human body was made forbidden to use for any non-medical reasons, otherwise the use of the magic is heavily restricted. 
- Known Members:
- Nakura Saburou (名倉 三郎)
- Once the Nanakura (七倉) Family, the name was changed to Nakura (名倉). The Seventh Laboratory's development focus was colony control magic that is able to move over 100 objects simultaneously but the projectiles need to be prepared beforehand with a spell to manipulate them. Nakura finds it combat ineffective to always have the bulky medium in hand so they developed Magic Sequences that could use colony control magic at any time at the expense of reducing the number of targets that they control and using any projectiles like water or even blood. Since they were unable to develop the ability that the Seventh Laboratory hoped for, they were stripped of their Number.
- It seems to be popular belief that the Nanakura's now serve the Saegusa Family, one of the current bearers of the number Seven (七) in their name.  However, this needs further confirmation, especially since it is explicitly stated during the conversation when Mayumi tried to recruit Tatsuya to conduct an investigation into the case of Nakura's death that "The police requested those, since they want to store them as evidence. Furthermore, Nakura-san has no relatives, so I thought it might help to catch the criminal even a little if I handed them over." 
- Kanou Shiori (十七夜 栞)
- When Shiori was younger, she was from a family that had lost its number and been an Extra. Though she has now been adopted by the Kanou Family, one of the Hundred Families.