In this chapter, the author explored the dynamic development of language teacher identity, focusing on how teachers self-identify their expertise through talk-in-interaction. Traditionally, teachers with less than one year of experience were labelled as novices. However, the teacher identities ascribed by such an external categorisation frequently diverged from the ways in which these teachers construct their identities through narratives. The study examined the evolving identity of Hana, a high school English teacher in Japan, through three interviews conducted over 18 months. Using longitudinal conversation analysis, the study highlighted Hana’s shift from a self-critical novice to a teacher who prioritised student comprehension and diagnosed her students’ English ability. The findings indicated that even teachers with short experience demonstrated their profession, expertise, and a sense of ownership over their students. This challenged the conventional portrayal of novice teachers as vulnerable and emphasised the importance of allowing teachers to express their evolving expertise through narrative. The study suggests that relying solely on pre-existing categories to identify teachers may not fully capture the complexity and nuances of their growth of expertise. Allowing the teachers to express their voice, particularly through narratives or talk-in-interaction, is significant in understanding the development of their teacher identity.