In the anime, not much is known about Daigo, except that he is famous for being a "legendary fighter". Daigo is a playful character and stands up for justice. During his anime début during Cardfight!! Vanguard: Asia Circuit, he is trapped in a space-time warp due to his clan, the Royal Paladins, being sealed away. This causes him to be the only Royal Paladin user until the conclusion of that season. He later reappears during Cardfight!! Vanguard: Link Joker, where he offers a ride to Kourin Tatsunagi, when she was running late to perform in a school play. He is then caught up in the play in a villainous role, and fights Kourin.
In the live action TV drama, Stand Up! Vanguard, Daigo is a wandering, self-proclaimed ally of justice, and a self-proclaimed genius, who claims to have studied at "HarvardA University", with a degree which reads "YOU ARE JUSTICE". Unlike his anime counterpart, he does not initially know how to play the Cardfight!! Vanguard card game, and his victories can be attributed to incredible luck. Happening upon a young boy called Hiroki Miura being bullied, he sets out to right this wrong, despite the boy's resistance. Through his convoluted efforts, he is hired as a teacher at Hiroki's school, as Hiroki's personal tutor, and finds a love interest in Hiroki's class teacher, Maria Kagami. Declaring himself Hiroki's apprentice at the game card, he convinces the boy to enter a tournament to stand up to his bullies.
In the live action movie, Cardfight!! Vanguard Movie: The Three Games, the same character as in the TV drama reappears as a teacher and colleague to Maria Kagami, and also as his school's Vanguard Club supervisor. Since his prior appearance, his deck, game skill, and reputation have improved to match his anime counterpart, and he demonstrates a vastly calmer playing style. As per a terrorist group's demands, the police enlist him as the "adult who is strongest at Vanguard". He is then forced by bomb threat to participate in three games monitored by the terrorists, including a puzzle, and a cardfight in which he could not use his own deck.
In episode 119 of the anime, Daigo uses a new Royal Paladin deck, with cards from the structure deck DAIGO Special Set. It centers around Sanctuary Guard Dragon and calling Grade 1 or lower units for the activation of Sanctuary Guard Dragon's Limit Break.
In this movie, Daigo's own deck is similar to his second anime deck, which centers around Sanctuary Guard Dragon. Unlike his anime deck, it contains Blaster Blade, a card considered extremely rare in the anime.
Even if a great number of years pass your fighting spirit will never waver! Ride The Vanguard! White Dragon Knight, Pendragon!
Do a fantastic jump over the limit with a marvelous leap! Pendragon, Limit Break!
Guardian deity of the knights, give your power to Pendragon, the king who commands of all dragons! Superior ride The Vanguard!
Pure, proud knight! I ride White Dragon Knight, Pendragon!
Spread the wings, ancient white dragon knight! Pendragon, Glorious Wing Limit Break!
From the absolutely beautiful, sacred world, swoop down on luminous wings! Sanctuary Guard Dragon!