The question asks about the specific term for Kripa and Karan's unique way of speaking a particular dialect of Manipuri, even though they are twins and share the same base dialect.
An idiolect refers to the unique, individual way a person speaks. It encompasses their personal vocabulary, grammar, pronunciation, and intonation patterns. Think of it as your linguistic fingerprint – no two people have exactly the same idiolect, even if they belong to the same community or speak the same dialect.
Since Kripa and Karan are twins and speak the same dialect of Manipuri, but they "differ in their speech," this difference points directly to their individual speaking styles. Their unique way of speaking that specific dialect is precisely what is termed an idiolect. Even identical twins, growing up in the same environment, develop slightly different speech patterns over time.
Therefore, the special, individual way Kripa and Karan speak their particular dialect of Manipuri is known as their idiolect.