I ordered it in the middle of last month, and as you can see in the top photo, the enclosed bonus item states, "One of five cards, chosen randomly."
However, the website states that you can only purchase up to six boxes to maximize availability...
Well, I thought I'd buy six boxes and complete the set, and hope to at least get a Niigata Akane card...
But the result was...
...I got a complete set, and two Niigata Akane cards!!<img src="https://storage.googleapis.com/oshinoko-5xfoy/oshinoko-5xfoy/admin-console-images/Em_97.png" alt="" height="28" width="28" fetchpriority="high" class="mx-2 mt-2 inline-block align-bottom">

[Oshi no Ko] x Saikatei River Steam | クロノア's post