The top lesson here is the pattern of guarded squares formed by these Knights. They are one Kt move apart, and they guard an "L" shape of 4-squares: a7, b7, c7, c8. This confines BK to a8 & b8. Let's see if the Kt's can be fixed, and if we can move only the K & B: 1 move each.

We know B can only mate on the long diagonal of his color (light), and the only square 1 move away on this diagonal is d5. We know the other square (b8) must be covered too, and that leaves WK for b8. Where can WK move to guard b8? Only c7. So BK moves to c7, and B moves to d5.

The only point left is, "Which moves first?"
Suddenly, it seems so simple! 🙂