One of the first character interactions we see in Undertale is Toriel unknowingly attacking her son to save a human child she does not know. She leads the human through the Ruins by their hand to keep them safe (from dangerous monsters like her son) and prepares a room in her house for them to stay in (like the one her son lived in). We can call her “Mom” and she will let us (Flowey watches us the entire time.) She attacks us so we don’t leave (the Underground is full of dangerous monsters (like her son)), but when we make it out, Flowey is there to criticize what we’ve done (we’ve taken his mom) (we’ve killed his mom) (we RESET to save his mom) (our mom). She doesn’t know who he is. He put her to bed when she’d passed out on the floor and left a glass of water on her table (someone has to take care of these flowers).