Based in Salt Lake, O‘ahu, and branding his instruments ASD, (I don't see this being used outside of his own website?), he started his instrument making career in the late 1990's but is still not a full time luthier.
As far as I can see all of his Ukuleles are Tenors and they are far from traditional in their design. He make solid body electric Ukuleles as well as acoustic ones but they all have his distinctive headstock and saddle/bridge setup, (well the older ones have a traditional type bridge but for some time now he has used the individual saddle design). The ‘オ’ on the headstock is the Japanese character for the phonetic sound ‘O’ as in Ogata.
From what Ive seen he mainly makes acoustic Guitars but has made some Ukuleles too. He was working in Kenji Sugita's workshop, having apprenticed at Ervin Somogyi Guitars, and in 2013 was allowed to start making Guitars under his own name. He now has his own workshop and I believe he is based in Takaoka, Toyama Prefecture but he also spend a lot of time in the U.S. So far I have only seen 12 fret Soprano Ukuleles which all have a distinctive notch in the headstock
Based in Hakodate, Hokkaido he makes Soprano, Concert and Tenor scale Ukuleles starting in 2005. His Ukuleles come in a variety of woods, can have slot or flat heads, zero frets sometimes but always have bone saddles and a carbon fiber rod in the neck. I have seen a 5 string double G Tenor model but no other string options, no pineapples and no other body shapes; I have see some imaginative sound holes though including a map of the Japanese islands in the same vein as some people do with the Hawaiian isles. In 2013 he started making a Tenor model with no top soundhole and a piezo pickup he called "Desire". I have seen suggestions of other model names too like Kaiser and J Storm but I'm not sure they are right there is no mention of them I can see on the website?
I believe his brand is Koa Rhythms and he is based in Kona on the Big Island. He makes 8 to 10 instruments a year and has been making them since 1999. I have only seen Tenors but I have read he makes Concerts and Baritones as well but not Soprano?