Rakuten Bank linked with Rakuten Securities – Myna Card link?

I have recently set up a Rakuten Bank account and linked it to Rakuten Securities, so that I can keep everything separate from my Japan Post account.

(I think) my Japan Post account has my myna info, and that account is where I receive all my salary, and pay for my credit card.

Do I need to link my myna card to my Rakuten Bank account also because it is transferring money for the NISA investments via rakuten securities?

Is it even allowed to have Myna linked to more than one bank?

by Drar