Tristan is a blue-haired female mink with a squirrel-like face and a large, bushy tail with two stripes down the center. She wears a short, light-colored dress and a nurse's cap with a cross on it along with red shoes with heels.
As a nurse, Tristan does her job in tending to the injured, though she believes that doctors like Miyagi should not be overly enthusiastic when tending to their patients or learning from other doctors.
Tristan is scared by strange people, having run off in fear after seeing a skeleton and a dragon talking to each other.
After the Straw Hats fought off the Beasts Pirates, they wondered where Tristan had run off as Tristan watched them from behind a tree.
After Caesar neutralized the poison gas, Wanda attacked Nami, thinking that she and her group were with Jack, but Tristan and Pedro calmed her down by revealing that they were not the enemy. With Chopper directing them, Sanji's group and all the minks that could move began to treat the injured.
Later, as the minks continued to recover from the Beasts Pirates' assault, Tristan observed that Sanji seemed to like greeting people as he went around displaying affection toward the female minks.
When it was reported that Duke Inuarashi had woken from his coma, Tristan followed Chopper and Miyagi to tend to him while telling Miyagi that he was being too enthusiastic. At the duke's home, Tristan, Miyagi, and Chopper tended to the duke until Wanda brought the rest of the Straw Hats. When dusk arrived, Tristan and Miyagi fell asleep.
The next day, she requested to join the Sanji retrieval team as Chopper's assistant, but was turned down in favor of Pedro since he could keep Pekoms under control.