This reminds me of the security guards' friendship with Missy (Chibi's OC). Vincent, at first, gets a bad feeling about Missy, but he eventually trusts her. But, when he finds Missy's secret, he loses his trust in her.

By the way, the image of Sans and Frisk drowning. I think it's symbolism to death. When someone dies, they sink into an endless ocean where they don't have the power to swim back up. If someone revives them, they will pull that person out of that ocean.

Video by Missy (Nek-0x).