Its says in mangaupdates that this series is completely scanlated but I didn't see volume 11 in there. Supposedly, volume 11 is the last volume of this series.

Is this some kind of a mistake?

Depends on how they define scanlations.

All 11 volumes have been completely translated by Del Rey. All BYAAAH has been doing is scanning in those books, and he just hasn't done the last one yet. If you don't want to wait, you can go out and purchase it.

So, no it hasn't been completely scanned, but the English copy is finished.

Incidentally, I was just thinking about this. Sadly, you're not allowed to ask for scanslation status.

Doesn't count as completely scanlated then

Series info changed to reflect this

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