The recent advancements in AI technology allow AI to communicate and interact with users more deeply. The experiences that AI service agents create for consumers have rapidly expanded, from transactional exchanges to more emotion-based interactions that integrate conversational or relational norms from interpersonal relationships. In particular, this chapter is centered on the relational role of AI service agents and the implications they bring. Specifically, this chapter looks into recent studies addressing the questions of (1) when do consumers perceive AI agents as relational AIs, in other words, relationship counterparts?; (2) how do they respond to relational AIs and their relationships formed with them? In doing so, the distinction between relational AI and the mechanical, thinking, and feeling AIs, as established by previous studies, is considered. Future research directions are proposed for deeper investigations into the impacts of social/relational roles AI agents play in various service encounters.