Yes you should not. If you want the level 5 S.E and 1167 atk(after ex)/1468 atk(after infinity ex) then dont until after you unseal it.
2011 kills unseals the sword.
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This was changed in Infinity. The final stats and SE level will be the same for sealed weapons regardless of extend/super extend/unseal order. In fact, if you plan to super extend it you should do that before you unseal it so that it's somewhat useable while you're unsealing it.
Found some stuff over the past few days:
http://i.imgur.com/qVVgD.png http://i.imgur.com/eUYTr.png
Magatatara Blade Pair: Tiger/Naval Goodbye
http://i.imgur.com/oqgzX.png http://i.imgur.com/vg9TF.png
Eight Ounces/Sealed Nodachi
http://i.imgur.com/zfGem.png http://i.imgur.com/cTDEh.png
Sega Genesis/Gale Bringer
That Fuuin Nodachi looks pretty cool, I guess that means its unsealable as well?
Edit: or not. :D Those stats are pretty lousy for such a high level weapon then. :(
It just says that currently no unsealing method has been discovered yet.
Ran Mad Beasts for 2 hours and got:
15* :neutral: Celestial Flame
2nd best Twin Sabers in the game. :D
Finally rebirthed for the first time from level 200. Maxed out tech and laughed as I beat Gemaga at level 1. Easy 20 levels.
Second Best? Interesting that it drops from Mad Beasts.
What class?