Tan and his family suffered under the oppressive rule of the Cardassian occupation of Bajor. While Starfleet wasn’t exactly seen as savior, they were in Tan’s estimation a better alternative until Bajor could regain its independence. He had plenty of opportunity to practice his Mother’s teachings (she was the closest thing their d'jarra had to a healer/doctor). Tan’s father did not survive his time on Terok Nor. During the Dominion war, a sixteen-year-old Masu Tan was caught unexpectedly in a battle, and during that time saved the life of a human. Tan didn’t know it at the time but the woman was a high-ranking officer in Starfleet and offered to sponsor him into Starfleet. Tan later took her up on that offer. He continued on the medical track, preferring to save lives where possible.

Tan does not adhere to the Bajorian religion, and tends to keep to himself. He is a hard worker, and has a peculiar sense of humour.