Japanese-developed game with the most disappointing 2013 sales?

[Barozi]

Hard to say. I knew Puppeteer and Wonderful 101 would bomb sales wise, but that doesn't make the sales less disappointing.
Lightning Returns did also as expected, but that's Japan only and with the other regions it should get decent enough sales.
Sonic Lost World did terrible. Considering they only share the same name, I'm not sure if they should even be combined sales wise. The exclusivity contract was a disaster for SEGA so far and I doubt that it's going to change.
GT6 did also well below any expectations. Still enough for a quick cash-in, although on the expenses of the fanbase.
The other Japan only titles have done terrible as well it seems. But I'm not into the handheld or Japanese market that much, so I better don't comment.

My choice would be Sonic Lost World, because it looked great at first and then turned out to be a lot worse.
Also SEGA voluntarily chose to partner with Nintendo instead of going multiplat as usual, which would've added the remaining sales to profitability.