Nose,

“Pine Tree,” Bill started and he took the heart from Dipper. “I…” He made an annoyed sound from the back of his throat and shifted again to look at Dipper with a concentrated expression on his face. “I’ve seen humans do this for thousands of years and I’ve read it in Shooting Star’s books but when it comes to actually doing all of this…” He made the noise again.
Dipper gave Bill a confused look, “What are you trying to say?”
“This!” Bill said, holding up the heart dramatically in air. “This!” He practically shoved the heart in Dipper’s face, “I’m this you!”
“Okay, you’re getting hysterical,” Dipper declared as he took Bill’s wrist and pulled his hand down, taking the heart and setting it carefully aside. “Just…breathe.”
“I can’t!” Bill yelled.
“Bill!” Dipper yelled back.
Bill put his hands on Dipper’s face, cupping his cheeks and leaned forward. Bill leaned forward and paused. “Nose,” He mumbled before tilting his head slightly and kissing Dipper.
It was clumsy and sloppy and absolutely obvious that Bill didn’t know what he was doing but he pressed onward in his attempts to kiss. Dipper took this opportunity to kiss Bill back, managing to take control of the kiss while settling his hands on Bill’s waist. Bill gasped and pulled away slowly when Dipper sucked on his lip and he looked surprisingly flush in the blue light of the fireflies.
“Uhm…”
“Yeah.”
“We’re covered in blood.” Dipper mumbled.