The Ainu: Caucasoid or Mongoloid?

Travel Info
I look at the pictures of many modern-day Ainu and a lot of them look quite Mongoloid. However, I have seen pictures of more pure Ainu and they look quite Caucasoid (like Middle Eastern). For instance, look at the Japanese singer Ken Hirai, the guy doesn't look anything like an Asian. If I saw him on the street I would think he is Iranian or something like that. What do you guys think?

Travel Tips

Ainu inu is close to Jomon people in the DNA level. There is no exact proof Ainu hold the DNA of Caucasoid. However it is said Caucasoid mixed with Mongoloid in Russia and Central Asia. If some descendant moved Hokkaido, some Ainu may inherit Caucasoid or Russian genes.

In 1264, conflicts erupted between Ainu and Nivkh (Russian minority). The Mongol, Kublai Khan's era, sent a military to the conflict. After that it is said Ainu hold tributary relationship with the Mongol.
Some Ainu and Nivkh ppl were living in the Karafuto island (Sakhalin). This island is north of Hokkaido. Japan governed the southern part of this island for a while. And a portion of Ainu and Nivkh took Japanese nationality then. After WW2, The ppl who have Japanese national sent back to Hokkaido, including Ainu and Nivkh who was Japanese then.
Now it is very hard to distinguish who is real Ainu and Nivkh. They didn't have a letter in their life.

Ken Hirai is not Ainu. He was born in Osaka, and tons of Okinawa ppl have moved to Osaka. He may have any gene of Asian Continent or Pacific islands.
Others

The origins of the Ainu are unknown. Some scholars claim that they are descendants of the Jomon people of Japan, and others claim that they are descendants of Mongolians and Eastern Russians. It appears as though they definitely do have Mongoloid descendants, though, since both Mongolians and the Jomon are placed in the "Mongoloid" racial category.
http://www.pbs.org/wgbh/nova/hokkaido/ai...
http://en.wikipedia.org/wiki/ainu_people...
Rabityama gave you the best answer regarding the Mongoloid question, but regarding your Caucasoid/Hirai comment:
Talk around Hirai always focuses on his ancestry. Pictures of his parents show they are typical Japanese an Hirai claims no other ancestry. I live in Korea, where all Koreans can be traced to 3 families: Park, Lee & Kim.
One glance around will tell you there is mixed blood somewhere, but it is culturally taboo to admit to it.
Part of Hirai's success has been his appearance. He has the western look so sought after by Asians who favor cosmetic surgery and other such shallow endeavors. To them, he has somehow been able to have the best of both: a western "pretty" face but retain JApanese ancestry.
I have never believed the second part, as I am sure most do not either.