Please recheck your sources guys, This is the 1st and only mention of "Howling Octave" in Volume 8
"The one-handed sword eight combo sword skill «Howling Octave». Its attributes were forty percent physical and sixty percent fire. Within the one-handed sword category, it was in a high tier."
Note: "high tier", OSS are unique and are not included within the rankings of normal sword skills. Also whenever someone used an OSS, it was specifically mentioned to be one.
"7 Deadly Sins" is not an original sword skill, there is no mention of it being an original sword skill
if you were refferencing this line
"This was Kirito's own skill that was created outside the system, called «Spell Blast»"
Please have a closer look at this one
"Kirito's specialty in old Aincrad was to use the sword skills to attack the weak points of the enemy's weapons instead of attacking the enemy, the outside system skill called «Arms Blast». Though that amazing skill itself required superhuman reflexes and extremely intricate aiming skills, it was harder to slice spells here in ALO. "
This entailed using already existing sword skills to slice through magic. The next line should serve as proof, unless of course "Kirito developed OSS to slice magic for multiple situations", He doesn't have the time to, considering he hasn't recreating all his "Dual Blades" skills. (it's mentioned in the interview)
" However, it was already beyond insane to try to capture the center of the spell when using a sword swing that couldn't be controlled due to system assistance, and almost impossible. "Kazakiri (talk) 23:47, March 24, 2013 (UTC)