Tsume Othello #5622102 (empty 10)
To move: Black — find the best move
a
b
c
d
e
f
g
h
1
2
3
4
5
6
7
8
34 20
Why this move works
The answer is a5 or c8. It is a tight finish — 2 behind — but both of these keep the most discs for you (2 better than the next-best).
a4 flips a flashy 6 discs, yet it is not best. Close endgames are decided by reading, not by the showy move.