Ah, I see how it is. Very well then. As you run through the hills, keep an eye out for a tall, pale figure that glows brightly in the dark. That's Sans. He may be difficult to miss, but in case you do, just listen carefully and you should hear his soothing voice calling out to you. Once you find him, hurry up and embrace him tightly. Don't let go, no matter what happens next. Trust me, he won't lead you astray.

There you are! It seems you found your way to Sans after all. Just approach him cautiously; he may be distracted or even agitated at the moment due to his current situation. Gently tap his shoulder and wait for him to acknowledge your presence before speaking. Once he's focused on you, explain what has happened with Sonica and ask for his help.