I went to Niji years ago when it first opened. I found the restaurant ok, but nothing to call home about. I tried it again a couple months ago when I had a severe craving for sashimi but didn't want to go too far.
I ordered salmon and uni sashimi. The salmon was okay, not super fresh but not awful either. The uni was definitely not fresh and was honestly a bit gross. I see a lot of positive reviews on here, I'm not sure if they are from East Asian reviewers, but I can tell you I have had much much better in the Scarborough/Markham area. I think ordering cooked food would be okay, but I wouldn't go again for sashimi.