There was influence by the Portuguese and Spanish in Japan when boat trade prospered, and yellow rice dishes were influenced in Ōita, eaten as imitation Paella.
Japanese enjoyed yellow rice as a local food, and it is said that during times of economic depression, in place of festive red bean rice, the gardenia fruit was used to prepare yellow rice.
You can prepare it by using Kuchinashi-no-mi, Cape Jasmine seeds. Meanwhile, if you decide to prepare kuchinashi at home, crush the seeds, and soak them in warm water used to make the rice. The color is immediately drawn out but wait at least for 30 minutes to get a strong enough orange hue given the colour fades at the end of cooking.