This is another one of those quick and simple dishes I make from leftovers. When I stew chicken wings or chicken breast, I have been re-using the simmering liquid (adding a mixture of mirin, soy sauce, and black vinegar in 1:1:1 ratio as I cook a new batch). After stewing a few batches of chicken wings, the amount of protein or collagen in the simmering liquid is high enough to make a nice gelée or "nikogori" 煮こごり in the refrigerator, so I decide to use it.
I just cubed cooked chicken breast, cucumber, and the gelée of the simmering liquid and topped it with mayonnaise with Japanese 7 flavored red pepper. I also garnished with fan-cut cucumber and perilla . The gelée really made this dish since it has nice slightly sweet, mild vinegary and salty flavors which come in bursts as you taste the small cubes of the jelled simmering liquid. If you have to make the gelée from scratch, I suppose you can dissolve either gelatin or agar-agar in the simmering liquid but that is probably not worth the effort.
In any case, the addition of mayonnaise further takes the vinegary edge off and this dish will go with any drink.