All Men Are Equal is an inhibition ability that allows Fukuzawa to suppress the abilities of his subordinates, particularly official members of the Armed Detective Agency. This means that applicants must pass their entrance exam specifically catered and prepared for them in secret, which is the standard application procedure of the Agency to measure their values and character. Otherwise, they would not be included in the range of the ability.
For instance, it has been activated on Atsushi Nakajima eventually after he passed his entrance exam, which from then on allowed him to partially manifest his tiger limbs with relative control as compared to his initially uncontrollable tiger transformation. Moreover, the ability has been activated on Kyōka Izumi following her successful entrance exam, which allowed her to use Demon Snow at a crucial moment without having to rely on her intermediary phone like she used to. Similar to Atsushi's case, Kyōka thereafter has considerable control over her ability due to All Men Are Equal's activation.
Furthermore, it is quite possible that All Men Are Equal allows Fukuzawa to know his subordinates' statuses. Specifically, after Doppo Kunikida fell from the sky during their escape from their pursuers, Fukuzawa knew that Kunikida is still alive after his grenade detonation – despite not being told directly of his condition – as he claimed that he would have felt it if Kunikida had not survived the blast.
The ability is derived from An Encouragement of Learning (学問のすすめ, Gakumon no Susume?) by the real-life Yukichi Fukuzawa. Spanning 17 volumes, the texts highlight the importance of equality of opportunity and of education as a vital key to success. These publications also outline independence as the goal of any individual and nation, as well as the transformation of the Japanese mind as it traverses a constantly changing cultural and political climate.