Farfarello, a demon from the Malebranche clan, serves as one of its current chieftains. His appointment followed Demon King Satan’s conquest of Ente Isla, making him the clan’s youngest chieftain. His demon form features bat-like wings and large, sharp claws on his limbs, though his face retains human-like traits. For human infiltration, he adopts a Showa-era Japanese disguise: an unpolished dark blue suit unsuitable for summer, silver spectacles, hair gel, and a black briefcase, appearing as a youth in his late teens or early twenties.

After fellow chieftain Ciriatto failed to retrieve Demon King Satan (Sadao Maou) from Japan, Farfarello deployed alongside Erone, a Gevurah Sephirot entity. Using Erone’s barrier magic to isolate Maou, Farfarello implored him to return to the demon world. Maou refused, citing unfinished business. When Chiho Sasaki arrived, Farfarello speculated Earth’s influence weakened Maou’s resolve. He supplied Maou with condensed demonic magic from Erone’s armor.

Their encounter shattered upon the arrival of hero Emilia Justina, inquisitor Crestia Bell (Suzuno Kamazuki), and fallen angel Sariel. As Emilia attacked, Farfarello commanded Erone to retaliate, overwhelming Emilia and Suzuno. The Yesod Fragment Alas Ramus unexpectedly reacted to Erone’s presence, merging with Emilia. When Sariel’s "Evil Eye of the Fallen" struck Erone, Farfarello retreated temporarily but vowed to reclaim Maou.

Later, after Maou declined to clarify his ambitions during a barista lecture, Farfarello directed Erone to abduct Chiho for interrogation. On the Tokyo Metropolitan Government Building rooftop, Chiho agreed to cooperate to prevent disaster. Farfarello reverted to demon form, disconcerted when Chiho fixated on Erone’s clothing beneath his armor instead of his monstrous appearance. Her composure—and her revelation she remained conscious during Maou’s prior transformation—nearly led him to mistake her for Emeralda Etuva. During interrogation, Chiho advocated human-demon cooperation, a concept Farfarello struggled to grasp. Their conversation ceased as Erone’s barrier broke, allowing Maou, Emilia, and Suzuno to intervene.

Farfarello apologized to Maou, explaining he sought only to understand Maou’s experiences and plans for Ente Isla. Maou revealed his focus on Earth’s monetary system as a solution for the demon world. Witnessing Maou’s temporary restoration to full power—through holy magic conversion facilitated by Chiho—filled Farfarello with remorse for doubting him. Maou then instructed him to return to the demon world and announce new demon generals: Alciel, Lucifer, Emilia Justina, Crestia Bell, and Chiho Sasaki. Maou provided a demonic magic orb, acknowledging the demons’ greater need. Renewed in morale, Farfarello departed with Erone.

Subsequently active in Ente Isla, Farfarello and Barbariccia met Alciel (Shirō Ashiya) at Heavensky. They explained their mission to retrieve a sacred sword and revealed Yesod Fragments react to demonic magic, not just holy energy. This prompted Alciel to enlist their guidance to Nord Justina’s quarters.

Notably, Chiho persistently mispronounces his name as "Farfarellao-san," leading Farfarello to abandon corrections after three attempts. Libicocco refers to him as "boy Farell."