This Japanese restaurant-chain is originated from Japan; their first restaurant in Japan was established in 1958. The restaurant has spacious seating layouts. So, people from other tables can't really hear your conversation. Straight to the food, I would recommend the following:

Appetizers: Hotate or Caesar Salad
Main Courses: Sumidon (beef over rice) or Oyakodon (chicken and egg over rice), Hokke or Saba fish, Cold Udon/Soba or Okosama Udon (they also have sets for noodle)
Rice: Hijiki Seaweed or Jakko Fish Rice
Side Dishes: Korroke (Croquette)
Desserts: they have variety of Japanese desserts that you could try

Their staffs also provide pretty good service. You could see some Japanese customers have their lunch/dinner in Ootoya; it shows that this restaurant serves good Japanese food in the Mall.