A little help with a guest singer!

First of all, hello to all you fans of this great singer!

So, I need help with this: A long time ago I downloaded a high definition video of Ken Hirai and a male guest (and old) singer singing Hitomi Wo Tojite live, on what looked like a radio program show. The guest singer was playing guitar, and singing together!

I'd like to know the other singer's name, and if possible, a way to download the video again (dont need to be high definition... I just NEED to listen to this duo again!)

Anyone can help?

Thanks from Brazil,
Diogo.