Kaya is a dog that belongs to Tzuyu. Her and her child Butter was adopted by Tzuyu and is currently living with her at her dorm. When naming her dogs, Tzuyu wanted to go with names go as a set since Butter and Kaya are both child & mother.
Nayeon suggested naming things that she likes or foods; in the end Tzuyu decided on naming Butter and Kaya (jam), which is derived from Kaya toast, a famous breakfast dish originating from Singapore. The dish was also mentioned during one of the episodes of TWICE TV6 during their visit to the country as they were visiting a supermarket.