Very cool. Yes, I suspect T's Guitars are a manufacturer for several Japanese brands, including Tkitki, Kiwaya (only some of the models I think) and formerly Takumi. However, the spec is very different for Kiwaya and Tkitki. I have Martin-inspired sopranos from both these brands and they are subtly different in terms of neck, fretboard, headstock, bridge, body shape. I suspect the plans are developed by the client and T's Guitars then produces to the desired spec.
Tkitki started as the premium house brand of TanTan ukulele, a small chain of ukulele shops. Kiwaya is a much older and bigger company with international distribution.