Supposedly the Japan “subsidiary” (if you can call it that) was set up by a Japanese person and a resident of Japan, who was a contact of SBF through the Effective Altruism thing. I think they knew something was shady, because the account they had opened in Japan was with a small rural Japanese bank.

When that “arbitrage” turned out to be really lucrative one of the founders of Skype (Talinn something) gave SBF a $50 million loan. SBF and that Talinn guy knew each other also from that Effective Altruism sect-like thing.

All this info was part of a Sequoia congratulatory piece on SBF, they of course had also given him money. The article has since been taken down, it’s still reachable through Web Archive.