Two green turtles in logo - what restaurant is this?
I just stumbled across the logo for Kappa Sushi, which is a kaiten place and does indeed feature two green creatures that could be interpreted as turtles. I've never been to one, since the web site lists the Tokyo stores as being relatively few and also all westside (Mitaka, Ome). Lots in Chiba and Saitama though.
More pictures of kappa here: