He talks about it around 4 min in, when they talk about the Gaim film. He says something like
"Those watching the show know that Helheim and Zawame City have some similarities - Kaito and Demushu are similar, and Mitchi also has a counterpart in Redyue. Also, Roshuo, the king, he's similar to Takatora. So these characters are similar, yet Kouta doesn't have a counterpart."
Jun: "Why doesn't Kouta have one?"
Gaku: "He appears in this movie!"
"Those watching the show know that Helheim and Zawame City have some similarities - Kaito and Demushu are similar, and Mitchi also has a counterpart in Redyue. Also, Roshuo, the king, he's similar to Takatora. So these characters are similar, yet Kouta doesn't have a counterpart."
Jun: "Why doesn't Kouta have one?"
Gaku: "He appears in this movie!"