It seems that that rumour was confirmed recently by the fact that ticket booking website eplus.jp is selling tickets for the Osaka card which lists the bout between Takayama and Odaira as well as the two bouts we've already had confirmed for the show involving Kazuto Ioka (15-1, 9), who fights Jean Piero Perez (20-7-1, 14), and Sho Ishida (17-0, 9), who defends his Japanese Super Flyweight title against Masato Morisaki (9-3-1, 5).
The website also states that Ryo Miyazaki (21-1-3, 12) will be on the card, as previously confirmed, alongside fellow Ioka gym fighter Takahiro Yamamoto (14-3, 11).
Although this is the strongest hint so far that the bout has been agreed it's not actual confirmation. We're now expecting that to come on Tuesday after Takayama's mentor, Hiroaki Nakade, stated that a press conference was set for tomorrow. We suspect that that will be to confirm the bout as being agreed.