I was unable to find even a bit of info on Seiko, other than that she’s an AV Idol.
Even my old friend Bobx, although it had photos—indeed it had all the sets that are floating on the inter-webs—didn’t even have measurements. That doesn’t happen too often. Although I suppose it’s by design, there are very few photos where her face is visible, and never a clear shot. In any case, it’s her body that’s the star and it’s quite scrumptious.