'An imaginary solution is one that, while theoretically possible, is practically impossible. There appears to be only one method by which a wife in Hokkaido can poison her husband in Tokyo. However, the chances that she pulled it off are infinitely close to zero. You see? The trick is doable, but pulling it off isn't.'
Slow anger, patience in revenge. A woman murders her husband by setting him up to commit suicide not only because he played a role in having her friend, who was his ex, commit suicide but also because he came to treat her in the same way.