Blurt out your true proclivities (Bottom route)

"I don't mind it all...the opposite in fact! I've been using a dildo for years now..."

You ramble on, blurting out more and more that you've never shared with anyone. You aren't sure if it's all the hiding of your desires over the years, but you can't help but speak candidly to Arya...perhaps more candidly than you should have all at once.

Arya looks rather shocked by the time you trail off into silence. Even if it's probably a relief that her futanari status is a plus rather than a drawback for you, she can't be finding it easy to the sudden knowledge that her respected, beloved older brother has been bouncing up and down on a dildo while fantasizing about getting nailed. She might need a bit of time to adjust.

You can tell that she's at least a little disillusioned; maybe not to the point of not liking you anymore, but her view of you has definitely shifted...though, you covertly notice that the bulge in her shorts has grown more prominent after your confession.

After baring yourself, and with Arya still at a bit of a loss on what to say, you're left with the choice; give her some time, or 'press your luck' and offer to help with the 'problem' between her legs.