This is a what-if fanfiction based on a bit of speculation about Orochimaru's sword, Kusinagi and the Japanese legend of Yamata no Orochi. You may ignore the Bible scripture at the end if you like, I'm not going to harangue you for it.
Warnings: AU, young Orochimaru.
Cain Slew Abel
By Kaori
Orochimaru hated Hebitaro.
Even though Orochimaru was a year older, even though Hebitaro was smaller and weaker, even though Orochimaru was smiled upon as the genius in the family by everyone and Hebitaro was only given sad smiles of sympathy, Orochimaru hated Hebitaro.
Why? Because Hebitaro was better at swordsmanship.
When Hebitaro was born he had significantly less chakra than was healthy for an infant and since then had never had the same chakra capacity as his peers. Hebitaro never could manage anything more powerful than a bunshin. However, what he lacked in chakra he made up for in sheer determination and will.
Orochimaru and Hebitaro's father taught them both the ways of the sword. However, Orochimaru was more interested in ninjutsu and genjutsu, and though he was no slouch with taijutsu, swordsmanship wasn't something he was interested in mastering.
Hebitaro, on the other hand, excelled at it. It was his passion, his life. As such, it always seemed to Orochimaru that their father favoured Hebitaro over him because while he'd dismiss Orochimaru after their two-hour training, Hebitaro would spend up to an extra two hours with their father.
He felt he was proven right when Hebitaro was given their father's sword: Ame no Murakumo when the man died. When he asked their guardian about this, he was told: "Your father felt that it was best to give Murakumo to the person who is best suited to handle it. You are far too course and your swordmanship is far too unrefined. The sword would do you no good."
Orochimaru was even more angered by this. Hebitaro was weak and inferior as a shinobi. How could his father entrust a sword to someone like that? He would take the sword by force.
A week later, he challenged Hebitaro to a dual. Whoever one would keep Murakumo for himself. Hebitaro agreed.
Orochimaru took advantage of every one of Hebitaro's weaknesses, especially his inability to perform offensive jutsu. However, Hebitaro's masterful swordsmanship pulled him through in the end and he prevailed.
Hebitaro was never able to celebrate that victory. Orochimaru, in a fit of rage, stabbed Hebitaro in the back with a kunai. Hebitaro, in his death throes, slammed the sword on the ground where it struck a rock and shattered. Orochimaru stabbed him again in the neck for his trouble.
When asked later what had happened, Orochimaru claimed that Hebitaro was attacked by enemies. There was a war on at the time and no one was going to question him, especially sine he had just recently lost his father.
In secret, Orochimaru had the sword re-forged and renamed it Kusanagi no Tsurugi.
"Now Cain talked to Abel his brother; and it came to pass, when they were in the field, that Cain rose against Abel his brother and killed him." – Genesis 4:8