Looking for a nice Japanese restaurant around Shinjuku district?
I recommend restaurant Mitsuya close to Shinjuku Gyoenmae metro station on Marunouchi line.
The chef(owner) used to cook for Japanese ambassador to Czech Republic in Prague and now offering Japanese cuisine with a reasonable price in Tokyo.
The restaurant itself is relatively small, capacity of 16 persons. Open daily except Sunday. Monday to Friday is open for lunch and dinner and Saturday is dinner only. They offer 2 kinds of courses too. Unfortunately no English menu available but the owner can help to translate.
I had an extremely delicious steamed oysters from Akoo in Hyogo prefecture. It was the best oysters which I had in my life!