And while we're dealing with cucumbers, I'd like to share this thing I do with it. I don't have a legitimate explanation for it but my mother and her mother did this all the time so I'm just keeping the tradition. Cut an inch off the head of the cucumber and rub both parts against each other. You will see some white substance (pulp?) emerging as a result. Apparently doing this gets rid of the bitter taste in cucumbers and yes, it is true.
Anyway let's get back to the salad: it is pretty intuitive but here's a rough guide if you're trying it for the first time.
3 cucumbers, quartered length-wise, deseeded, cut in 1/2-inch chunks
1 red onion, quartered and thinly sliced
3 tablespoons Japanese rice vinegar
2 tablespoons white fine sugar
1 tablespoon sesame oil
(Optional) 1 tablespoon lightly toasted sesame and/or torn-up sheet of Nori seaweed
1. Toss the cucumbers, red onion, rice vinegar, sugar and sesame oil in a glass bowl.
2. Sprinkle with toasted sesame and the Nori seaweed to add more texture to the salad.
When it comes to balance of taste, it's all about individual preferences. The above should not make you cringe, though.