'I am Leo's future self, who somehow ended up in this world and lifetime again.'
'Just like my past self, the Duke Apparent Leonidas was summoned to this world three years ago, it seems that this world was summoned to the place where I originally came from.'
'It's been three lifetimes since I last saw you, so you have no idea how glad I am to be able to meet and talk with you again.'
All of those would allow for a much simpler communication with Lady… No, with Agatha. But contrary to the way Leo actually introduced himself to the woman, they would all require a far more extensive discussion, proving stuff or revealing the stuff that Agatha wasn't ready to learn about just yet.