It's very simple. I love this place.
Kokoro is a small take-out sushi joint. It's true that their menu is somewhat small and the fish selection isn't as vast as other sushi restaurants that you can sit down and have a meal at, but the fish is always fresh and the sushi is always prepared excellently. (Note: There is a small table near the window that can maybe seat 3. This is really a takeout place, and it's not recommended for eating in.)
In addition to the freshness and tastiness, the prices are really quite good. Your standard rolls tend to range between $3 and $5. The real deals are in their sushi combos and 8/8 combo (8 pieces of sushi, 8 pieces of sashimi).
Lastly the service is always speedy. The folks that run this place know how to do it right. I've never had takeout sushi anywhere near this good, and I'd say Kokoro's sushi even surpasses most sit-down mid to upscale sushi restaurants in Toronto.
Bottom line - try it. It's fantastic.