User blog comment:B214/Volume 17 spoilers./@comment-16281343-20140220010926/@comment-3965848-20140222175456

That sword  could  have been Excalibur Mimic, as the sword itself is able to change it's form.

My guess is that sword in the photo might be Mimics "true form", and when Irina wielded it, she must have changed it into the form of a Katana.

That's my theory