Ken Takagi and his mother own the successful Coco’s Yakitori Sushi Bar on Westheimer. Now Takagi has opened another sushi bar called Sushi Tora (920 Studemont, 713-864-8672) just off the hopping Washington corridor. “Coco’s is a lot bigger. It’s 4,000 square feet. Tora is 1,100 square feet. At Coco’s the…