Sasuke Uchiha was 5 years old when he first realized he hated Shikamaru Nara.
"Wow, 100 points! Good job Sasuke!" his teacher said with a grin.
Sasuke let out a happy smile as he held his test paper,"Yay, I worked really hard on this!"
"Wow, you also got 100, Shikamaru, and you didn't even study!"
Shikamaru yawned before scratching his head,"Yeah, whatever."
Sasuke stared at the other boy, before crumpling his paper,"Shikamaru..."
Sasuke was 12 when he decided that he really hated Shikamaru.
It was a joint training exercise between Team 7 and Team 10, and Sasuke had found himself pitted against the young genius. "I can handle him." He decided. After all, Sasuke survived the Wave Mission, he could survive anything Shikamaru could throw at him.
Except, perhaps, being caught in a shadow and surrounded by bombs.
Shikamaru scratched his head, making Sasuke do the same,"Geez, you're really predictable, you know that? This was, like, plan 1"
"Don't you mean plan A?" Sasuke said, a bare hint of rage pouring through his voice.
"Why would I only have 26 plans?" Shikamaru asked.
"... Shikamaru!" Sasuke snarled.
Sasuke was 16 when he decided he wanted Shikamaru dead.
Sasuke stared down the group of enemies before him. He had already decided to aid Konoha just this once to achieve his goal.
At that moment, all the white Zetsus were burnt alive by a multitude of traps.
Shikamaru appeared behind him,"Well, that finishes that! Thanks for distracting them, buddy." He walked away.
"... Shikamaru!" Sasuke shouted.
Sasuke was now 30-something, and currently drinking with his fellow classmates at the reunion Naruto had dragged him into. He then took one look at Shikamaru,"You!"
Shikamaru looked back at him,"Yo."
"Our rivalry has yet to end, Shikamaru." Sasuke snarled as he stomped towards him,"My daughter will become a Chunin long before your son-"
"Sasuke?" Naruto asked behind him,"What is this?"
Sasuke looked behind,"Naruto?"
"... Do you have another rival?" Naruto whispered.
"Naruto, look, I never said I wanted to commit to this," Sasuke said.
"I thought we had something!" Naruto shouted,"Did all our fights mean nothing to you!? All our rivalries, all those times I desired to kick your ass, all that... and you had a side-rival!?"
"I'm not a one-man rival, okay Loser?" Sasuke said.
"Don't you Loser me!" Naruto pointed at him,"You know all those times I said I wanted to beat you, all those times I demanded a fight with you? My eternal love-hate of you!? I was faking!" He stormed away.