First, introduce a common goal for Ruby and the OC. It could be something like finding out the truth about the OC's father. As they work towards this goal, they will face challenges. Ruby's positive and determined attitude can inspire the OC, and in turn, the OC's personal journey related to their father can show Ruby a different perspective. Also, add some light - hearted moments, like joking around during training sessions or sharing a meal together. These simple interactions will gradually strengthen their relationship.
To develop their relationship, start with small shared experiences. For example, they could both be on a mission together and have to rely on each other's skills. Ruby's speed and combat skills, combined with the OC's unique abilities (which could be related to their father's influence), can create a bond through mutual respect. They can also have heart - to - heart conversations about their families, especially about the OC's father. This can deepen their understanding of each other.