Keith focused intently at the communication that was being delivered to him, only cocking his head slightly to the right, watching him then looking down at the sand drawing when needed. He thought he understood what he was told; Shiro, the merman himself, found trouble with this communication. He couldn't form the link when tired, and compared to a slightly similar species, he could barely even communicate to begin with. He did wonder about that other species, though, and he leaned forward more closely to stare. 

He rested his chin in his palm, head tilted until he took a wild guess and supposed that this was the kind of mer that were in legends in the past, luring seamen to their deaths. But with that thought, the necklace and his ability to speak at random times telepathically, there was but one explanation. Keith was related to sirens, or at least merpeople like Shiro. When the words came to his mind, it didn't pain him, but the idea of getting them to leave his mind was a chore. 

With a look of disbelief on his face, Keith reeled back a bit, before he slowly pointed at the siren and at himself, then at the mermaid and at himself, giving a shrug like he was ridiculing his own theory. He was unsure who he was at this point, but he really really couldn't be a sea creature. Where was his tail? Why was he so scared of the water if he was a sea creature? So many things didn't add up, and Keith took hold of his necklace for some balance, fingers trailing from one shell to the other.