Undertale: Last Breath

After many restarts and going down the same genocidal path about thirty times, you reach the last corridor, where Sans is. But instead of Sans waiting for you, he appears directly in front of you.
Sans: "Hey. Been busy? hehe, as always. So I have a question for you, but this time it's different. How do you think your actions changed the world?"
You don't say anything, Sans just keeps that smile
Sans: "You're still not being very frank, huh? Oh well, it doesn't matter. You can stop pretending, I know everything. What am I going to do now? Well, you'll see."
There is a moment of silence, with neither of them saying anything yet.
Sans: "Let's get to the point."
Then your imagination turns black and white, like one of those retro games without color, but you already know that.
Sans: "It's a beautiful day outside, as always. The birds are singing, the flowers are blooming… On days like these, monsters like me…"
Sans closes his eyes and changes his iris to a rather serious one.
Sans: "I can't afford to care anymore."
Sans proceeds to launch floating bones and Gaster Blasters at you, but in a different way than you're used to; even so, you manage to dodge them without taking damage.
Sans: "A nice reminder of the old days… more or less. But this is only the beginning."
Now it's your turn to choose what to do