While all of the above is true, it is not only a Rakuten Ecosystem problem.
In my case, my starting point is:
FirstName<space>MiddleN<space>LastName on Passport.
This as properly been converted to the Japanese approach on Zairyu Card and MyNumber Card to:
LastName<space>FirstName<space>MiddleN
I didn't have much issues, getting
Rakuten Securities, Rakuten Card and Rakuten Bank to get aligned, as they all required the name to recorded in the order and format of the MyNumber Card. Even Rakuten Ichiba followed suite.
However, Rakuten Cos ITs seem to have difficulties recording the space between FirstName and MiddleName, which means that technically they have recorded my as LastName<space>FirstNameMiddleN
(In all fairness, getting only FirstName<space>LastName on the physical Rakuten Card was no problem for me.
This now prevents me from using automatic sync/connect services with Rakuten. For instance changing the deduction account for Rakuten Card looks like a pretty straight forward process when using any of the ca. 8 pre-suggested banks. In (my) case trying to connect with SMBC however, the handover doesn't work, because "the number of characters" doesn't match! .... why? Because SMBC got it proper with the second space included, thus the number of characters for my name is one digit longer
Workaround is then likewise the paper account change form which needed to be requested via a lengthy phone call with Rakuten Card... workable but cumbersome.
Another example is
PayPay App, PayPay Bank, PayPay Card. While all sound like the same family, the services and their ITs have very different legacies. Connecting the PayPay Bank's account with the PP App only worked after a couple of rounds as PP Bank's IT likewise can't register a space between FirstName and MiddleName. Maybe I should frame the paper letter telling me, that PP Bank (which actually evolved out of the renamed SMBC online bank JapanNetBank) can't properly register my name.
Getting the PP Card to only show FirstName<space>LastName also took 3 rounds of card production....
A further example is
Sony Bank,
can't cope with space between FirstName and MiddleName either in their IT as they use a single field for it. This thus funnels through to the physical Sony Bank Wallet Card which now bears LastName<space>FirstNameMiddleN making it useless for most online payment services involving any element of sync as name consistency can't be established.
SMBC (Olive) was setup properly from the outset, but in order to connect the SMBC Visa Card via the SMBC ID (which is just an email address) also required introducing& aligning the middle name on the Card's records. Name change, I believe to remember, couldn't be done online, thus triggering a further paper round. Trying to connect SMBC Olive App with the SMBC's V-Point Service App disclosed that the V-Point App only allowed for 4+4 characters in the 2 name fields which completely prevented registering a match with the First+Middle+LastN concept.
I note however that two friendly phone calls with the V-Point service and the bank phone service lead to them sorting it out among themselves. 2 days later it was solved and works smoothly ever since.
Conclusion: Many IT systems don't provide for a proper reflection of the
First+Middle+LastN concept requiring two spaces! That seems to be the main flaw. I even heard of people convincing immigration to "delete" their middle name from Zairyu + MyNumber Card to provide for a consistent start.
In essence, a lot can be achieved if time and perseverance are spent. I am optimistic and a bit an admin-nerd and understand that most people would give up earlier!