Also known as: ギョク
Gyoku (玉) is the God of Hirano's Shrine and is Hirano Sakurasaki's yin-yang that has its own mind and thus can communicate with Hirano. It has spiritual power, so it allows Hirano to attack. It was first introduced in the C74 version of Banshiryuu as Hirano's support partner and "the second protagonist of this game". It's unknown whether it's male or female.
https://en.touhouwiki.net/wiki/Gyoku