3rd Kyū

To summarize, the starting and ending points of diagonals and anti-diagonals follow regular patterns.

First, here are the patterns for diagonals (↗ direction) starting from the a-file.

As the starting point moves up, the endpoint squeezes in from the right along the 8th rank.

Next, the patterns for diagonals starting from the 1st rank.

As the starting point moves right, the endpoint squeezes down from the top along the h-file.