I spotted an interesting bike on ebay, an evidently Japanese brand I've never heard of. It's decaled SEMAS, and the only thing I found with a quick web search is a Tokyo-/Kanto-based cycling club/team, and a few links to bikes based in Malaysia. So maybe Semas was a Japanese brand that got some traction in east Asia back in the day? Some/zero connection to the team? It's not ringing any bells with me, and I haven't had a chance to dig out one of my Japanese magazines to scan the backpages adverts.

I did a c&v forum search, came up blank. T-mar? Anybody? Bueller? Bueller? Anyone? Bueller?

To my eye this is a very cleanly-done frame, not at all uncommon from other higher-end frames sourced by brand-holders from smaller Japanese builders. I suppose it could also be a very clean build from a bigger mfr, like Miyata/Panasonic, though it feels more like a smaller-shop build. I'd think it could have been from Cherubim, but the stay ends on this one are French-style "fish-mouth," where the Cherubim ends were often Motobecane-style slanted cuts. I think there were likely many more capable small Japanese builders in the '70s-'80s than I'm aware of who could build to this level, even in a production frame. It's in my size wheelhouse, but I'm not in the market, have no connection to seller, yadda x3. And far be it for me to criticize others, but I really wish the seller showed us more of the frame details than the components---we know what ders/cranks/bars look like:
https://www.ebay.com/itm//303739014169