The initial Persona (初期ペルソナ, Shoki Perusona)? is the Persona that represents the most inner thought of its host. As a beginning Persona, its ability is usually relatively weak, so the mythological or historic figure that the Persona takes form is often less significant in the respective mythology or history, though there is some exception.
This is the first game in the series which has the more uniformed origins of signature Personas of the playable characters from only the Greek and Roman mythologies. All of them also have fashion design motifs.
This is the first game to feature initial Personas mostly from modern fiction or historical figures, whether proven or contested. Persona 5 Strikers is also the first game to feature an initial Persona that isn't actually a Persona, with Pithos.
* Although Goro Akechi's true initial Persona in Persona 5 is heavily implied to be Loki, Robin Hood is the first Persona Akechi summons while operating as a party member, and mechanically functions as Akechi's initial.
** While not actually a Persona but an entity or multiple entities very similar (making Pandora Sophia's actual first persona), Pithos is summoned in the same way as a Persona and fills the same gameplay role, being the first "Persona" Sophia summons as a party member.