Hm..... the idea of taming a person seems really strange, and then becoming physically strong just because you tame a strong person. Seems like a really strange permutation of a typical manga slavery story, like Roxanne and Sherry, mixed together with a typical kicked out of hero party proving-your-worth story.
All I can say is............ AHHHHHHHHHHHHH......... MhhhhMMMMMMMMMMMM!!!!