Deneb is an Imagin fully contracted to Yuto Sakurai, gaining a physical form within normal spacetime due to Sakurai's wish for the Imagin to aid his past self as part of their contract. Rather than possessing him to travel into the past, Deneb willingly betrays Kai and possesses Sakurai in the middle of a fight after witnessing his desire to protect time as Zeronos. Deneb serves as Yuto's butler and fights alongside him while he is in Altair Form, able to shoot bullets (or smoke pellets) out of his fingertips. He also provides Zeronos the ability to transform into Vega form. He carries around a basket that contains hand-made candies that have wrappers that bear his face called "Deneb Candy". His personality is the polar opposite of Yuto's, with Deneb's noble demeanor usually resulting in embarrassing consequences done to Yuto, who comically beats him up for it. Although Yuto treats him with occasional disrespect; Deneb chooses to stand by his side out of friendship and loyalty, knowing Yuto to be a kind person. He also acts as a parental figure to Yuto, doing his best to make sure he lives healthy, including a need to serve shiitake to him, despite Yuto's deep hatred towards it (and usually resulting in a comical beating). Due to the fact he has a physical form in normal spacetime, Deneb often appears in (poorly constructed) disguises in order to avoid standing out.

Due to Deneb's limited interaction with the Tarous, he does not have names for them. However, he has on one occasion called Kintaros "Kumagoro" and Urataros as "Kametaros". Deneb is also the only Imagin other than Ryutaros to call Momotaros by his actual name as opposed to a nickname. Deneb is also the only main Imagin who does not have his own catchphrase, although merchandise from Toei and Bandai often feature Deneb saying "Please take care of Yuto". Upon transforming into Vega Form, Deneb often starts out with "Let me tell you this for starters...", followed by something honest. The first instance was "This face on my chest is only a decoration!".

Deneb's physical form is based on the historical story of Benkei and the fictional Karasu-Tengu. He is also named after the star Deneb in the constellation Cygnus the Swan which is important in the legend of the Tanabata along with "Altair" and "Vega", the names of the two forms that Zeronos can initially access.