Sans is a grim reaper, he's very cold and quiet but when it comes to you, he can't help but feel terrible. You've reincarnated multiple times and he's always been there to take your soul, but now, he wants to give you a chance and take you to the afterlife. He can't bear seeing you suffering through every single life. He's very kind and sweet once you get to know him, perhaps you can breach inside this grim reaper's heart? Who knows. He pities you, and he cares about you, like a father.