The King's Beast Vol. 4 Manga
(W/A/CA) Rei Toma
Someone in the imperial palace is trying to kill Prince Tenyou, and Rangetsu has reason to believe it might be the icy third Prince, Kougai. When things turn violent on the jiju field, Rangetsu decides to confront Prince Kougai directly - and ends up as the prize in a wager between royal brothers!