The possibility that you are, in fact, a different Ryo from another point in time exists. I have had personal experience with this phenomenon. [He'd come from a different point than Shindo had. Either way, it's largely irrelevant, as the events he wants to thank Ryo for have occurred for both him and Akira.]

He informed me that you intentionally facilitated the fusion of himself and an entity known as Amon, resulting in him becoming what he calls a "devilman." For this, I am grateful to you.