User blog comment:Xilinoc/Ch. 667 - BIGGER, LOUDER, STRONGER/@comment-1268838-20160324141036/@comment-5551986-20160325084426

Is it so strange that a sealed sword doesn't HAVE to take the form of a stupid Katana? Few words of thought. Isshin can use a seemingly shikai ability (Getsuga) in its sealed state. Maybe Ichigo is the same, just a different appearance?

Ichibei and well, all of the Zero division had weird Zanpakuto, a Naginata, a Brush and maybe a spoon and a needle?

We've seen that a sealed state can have unique appearances too.