Even though he was abroad, he is bad at English and hates to speak it. Even while in America, he did everything in his power to only speak Japanese.
Unlike Ryoma, his favorite Fanta is orange flavored.
It has been revealed that Ryoga's reason for leaving the Echizens was because Ryoga was going to move into his Aunts' place.
In his locker, he has an orange and a note "Mada Mada Daze".
When he was very young, he visited Ryoma, with who he grew up together, to say farewell. He kept believing that if he continued tennis, he’d meet Ryoma again.
Ryoma left the American representatives at the same time as Ryoga fooled him about his whereabouts.
He has a comb that was being used by Duke. He borrowed it during the Japanese training camp, but has yet to return it.
Ryoga is the only character in the series to appear in a Movie before his anime and manga appearance. Ryoga first appears in movie The Two Samurai. He then appears in the anime episode The Prince of Naniwa First Act which is an OVA from the Another Story series which takes place just after the Nationals. After this, Ryoga appears in the manga New Prince of Tennis chapter 50. Ryoga then appears in the New Prince of Tennis Special.
In both the movie and manga, when he meets Ryoma, he has the same reaction and similar wording when Ryoma has forgotten him. He looks slightly shocked and quotes, "Don't tell me you forgot your older brother."
Ryoga is one of the few tennis players who are capable of hitting 10 tennis balls. 11 balls if you count the orange.
Despite being Ryoma's older brother, he does not list Ryoma as one of his family members.