No I watched it about 2 years ago, but I recently discovered (Due to a completely different series) That I am a romantic sap... then I started thinking about Sekirei and decided to rewatch it because this time I'll feel like reading the manga to continue on. And I thought "This would make a very interesting RP."
Well it is allowed, but it's harder to get accepted as a Male. We don't want too many Male Sekirei so they will be rated more strictly than others just like people who want to be a single number. So yes feel free to sign up as a male if you keep all that in mind.
Don't forget nobody's signed up as an Ashikabi yet, and there are no gender restrictions on them at all. I look forward to seeing your SU