Mario operates Garden Mario, a tavern and refuge within trade city E-05. Their gender-nonconforming presentation features a masculine physique contrasted with feminine attire: a pink service dress, white ruffles, a hair flower, and pink heeled shoes. Having never known a conventional home, Mario built Garden Mario as their own sanctuary, extending its shelter to nurture the community.

Stern yet deeply nurturing, Mario acts as a fierce protector, confronting threats to friends and commanding respect despite facing ridicule. The character formed a significant parental bond after rescuing Kidow before the series began, providing stability, and later extended similar care to Ilie during her stay.

Mario engages directly in major conflicts, participating in resistance efforts against a military coup during E-05's civil war, demonstrating courage and determination. Emotional depth surfaces through grief over lost community members, balancing vulnerability with resilience.

The narrative maintains intentional ambiguity around Mario's gender. They use a natural voice without pitch alteration, and characters employ varied pronouns. The story portrays Mario's identity through consistent actions and community relationships rather than explicit labels or exposition, leading to audience recognition as a potential transgender or non-binary character integrated without tokenization.

Mario reinforces their role as community historian and emotional anchor by sharing background information, such as details about Kidow's adoptive father Lazarus and his survival teachings in the Cagaster-infested Far East, with Ilie during the crisis.