Tachibana no Tomomasa serves as a Lieutenant of the Left Imperial Guard within the capital of Kyou. He holds the position of Byakko of Earth among the Hachiyou, his elemental attribute being Swamp, with his dragon jewel situated between his collar bones.

Tomomasa presents an aloof and easy-going demeanor, frequently displaying flirtatious and nonchalant behavior, especially towards women. Beneath this exterior, he conceals sharp judgment of character. He navigates interpersonal relationships with charm and wit while maintaining a perceptive understanding of others.

Within the narrative, Tomomasa develops a significant connection with Akane Motomiya, the Priestess of the Dragon God. He initially engages her through lighthearted teasing and flirtatious remarks, often causing her to blush. His feelings deepen into genuine care and enchantment with her presence and smile, leading him to regard their shared moments as exceptionally precious. In his personal storyline conclusion, he remains by her side and openly expresses his true emotions.

During the events of the Maihitoyo movie, Tomomasa plays a key role in confronting a vengeful spirit threatening the imperial palace. Seven years prior to the main story, he witnessed the sudden death of a dancer performing the Sairyou-oh dance. In the present, he investigates the spirit's identity alongside Eisen, determining it to be Oono Suefumi, the deceased dancer. He participates in protecting Akane during purification rituals and supports her through spiritual challenges.

Physically, Tomomasa is 31 years old and stands 183 cm tall. He possesses teal-colored wavy hair styled in a curtained manner and teal eyes. He is typically seen wearing traditional kimono attire, complemented by earrings and often carrying a hand fan. His blood type is B.