Henry Spencer wrote: If you look at the bottom of this MobyGames list (
http://www.mobygames.com/game/dreamcast/shenmue/credits) it actually gives us the answer to this, albeit not descriptive who does what but I recall looking into it a few years back and seeing some links between the developers, the staff within SEGA Japan do move around a lot (there's been so many division merges and renames it becomes really confusing trying to keep up with it all). I think that ultimately, it all comes down to the project leads that matter since there's so much shuffling around, so I agree that the link between Yakuza and Shenmue isn't as big as it's made out to be, just shares some of the same staff (Nagoshi supposedly when in the pre-production stages went around SEGA divisions showing off the Yakuza concept to all staff and whoever showed interest joined him to make it).
The other thing I found when looking into Shenmue's credits through MobyGames was that a lot of the staff just frankly disappeared from game development without a trace. So either they went freelance/contracting after this and went to work at somewhere like TOSE (a company renowned for never getting credit despite helping create some of the most popular Japanese video games of all time and having really talented staff) or they just left game development entirely. Always found that aspect of the development kinda fascinating.
Can't believe I was nuts enough to do it, but I've basically sat and gone through the credits for most of the staffers on Shenmue II.
You're right that a lot of developers just disappeared after these games, moved to a different division of SEGA (a lot appear to have worked on Sonic stuff), or just stayed at AM2 (surprising amount have worked on Miku games). Although others seem to have moved to Nintendo, Namco, Capcom, Sony, Konami, Square Enix, Mistwalker, Koei-Tecmo, etc.
That is, if they're actually the same person and not another developer that shares the same name. Yu Suzuki, for example, is weirdly credited on Mobygames as a designer on a Kingdom Hearts game from 2016 when we know that obviously wasn't the case.
Potential inaccuracies aside, the Yakuza links are still pretty tentative from what I can see. A few animators, sound designers, 3D artists, and support staff of various disciplines. They also seem to mainly be contributors from the PS3-era games onward, although some have dropped in and out over the years.
Myth busted, I guess?