Unfortunately, your photograph does not show the right side of the screen, where the specific model of your "Western Digital My
(Book?)" would be shown. It's hard to Google for problem reports or solutions for that specific drive on OpenBSD, when we do not know what it is.
I can also see that the expected kernel messages for the creation of a dynamic
sd(4) device does not appear on this photograph.
The
uhidev(4) driver manages keyboards and mice.