Okay, so imagine that Fox Man receives a giant Snickers bar for Christmas from his brother, but when Shirasu asks him what he got him, he's like, "Oh... crap," and he begins a search for his twin's Christmas gift.
(I laughed the moment I saw your URL in the inbox because I just knew)
"Merry Christmas, Brother."
Kotarou stared in awe at the gift his brother placed in his hands. It was huge, and that shape, could it be…? He tore the paper to reveal the giant Snickers bar within.
"I know how you’ve been searching for something like this, so I thought it was perfect!"
"Brother…" Kotarou stared at the sacred item in his grasp disbelievingly. There really were no words. “Thank you.”
Shirasu just chuckled, obviously pleased with his reaction. There was a moment of expectant silence as he watched his brother admire his gift, but as the silence stretched he started to feel a little awkward. He cleared his throat to get his brother’s attention, and when he finally tore his eyes away from the (giant) Snickers bar, eyes a little misty, Shirasu held his hands up to him in supplication. "And for me?"
Outwardly, his expression didn’t change, but inside, Kotarou felt a sense of panic. Oh, crap. Despaired as he had been over his inability to receive the oh so revered confectionery, he’d completely forgone obtaining a gift for his own brother. And now here he was, his own gift tightly gripped to his chest, and his brother, with that a small smile, waiting expectantly for his own gift. With a sick feeling in his gut, Kotarou once again looked down at the bar in his arms.
"Brother, are you me?" He repeated the question they'd shared between them since their childhood, his voice low.
"I am...?" Shirasu's voice trailed off, making his response sound like more of a question than a retort.
Kotarou drew in a slow breath. "If I am you, and you are me, then... this gift is also yours." With a sudden flash, the Snickers bar was sliced perfectly in half and, with a final resolved look, he offered one half to Shirasu, who accepted it wordlessly. "So... Merry Christmas, Brother!"
Bonus: Shirasu's reaction: 눈_눈 "u fuckin' serious, bro?"