Ryuji Sakamoto (坂本 竜司, Sakamoto Ryuji) is a character that originates from Persona 5.
in Persona 5, Ryuji is first introduced as a delinquent student at Shujin Academy, showing little care for the faculty, with a particular dislike for Suguru Kamoshida, the volleyball coach. He meets Joker when Kamoshida picks Ann Takamaki up in his car, and calls Kamoshida a pervert. Joker, not knowing about Kamoshida, inquires Ryuji about it, and, realizing he is a transfer student, Ryuji quickly talks to and gets along with him. The two accidentally come across Kamoshida's Palace, a twisted, darker variation on the school where a shadow version of Kamoshida is the king. Ryuji, almost killed, is ultimately the catalyst behind the awakening of Arsène, Joker's Persona.
The duo meet Morgana in the palace as well, who walks them through on the usage of Personas, and how to get out of the Palace. The duo decide to return to the palace later on, and Kamoshida reveals (through his shadow) that he intentionally injured Ryuji's leg to inhibit his abilities in sports, as Ryuji was a hindrance to his plan to gain admiration school-wide. This upset Ryuji greatly, and his Persona, Captain Kidd, called out to him to awaken his feelings of revengeance. As a Phantom Thief, he takes on the codename Skull. In battle, Ryuji uses bludgeons and shotguns, and he specializes in single physical skills and thunder spells.
As a background character
Ryuji also makes an appearance as a background character on the Mementos stage, dressed in his Skull outfit.
Ryuji appears as a part of the Phantom Thieves of Hearts spirit, as well as his own independent spirit.