The defense of the Philippines relied in japanese mercenaries. We could have a daymio being hired to defend Manila from chinese or dutch pirates. The daymio and most of his troops convert and come back to Japan.
The daymio grows ambitious and receives some spanish supplies, maybe he could start trading with the Philippines and Mexico. He grows powerful and some other local lords join him, convert to catholicism and get trading advantages. Finally the daymio becomes shogun or even defies emperor...
However I do not see either an spanish ruled Japan. Although it would have been impressive see some allied samurais tercios in the 30YW.
The daymio grows ambitious and receives some spanish supplies, maybe he could start trading with the Philippines and Mexico. He grows powerful and some other local lords join him, convert to catholicism and get trading advantages. Finally the daymio becomes shogun or even defies emperor...
However I do not see either an spanish ruled Japan. Although it would have been impressive see some allied samurais tercios in the 30YW.