When to go
The neon sign at Sixtyseven 六十七 can be photographed year round. Since it's an indoor location, the weather conditions won't affect how the restaurants looks.
The best time of the day to find similar conditions is at night when the neon sign will be more illuminated and you'll be able to capture a more moody vibe.
Field tips
Be respectful. The owners of the restaurant don't speak much english, but before photographing, ask them politely if you can take photos of the space.
Try arriving right before they close (midnight), so you aren't disturbing other diners.
Since there's low light in this setting, I suggest having a fast lens.
Bring along a model so you can take a portrait shot and breathe some life into your image, to compliment the neon sign.
Play with the atmosphere and light of the place. Take photos at other tables (as long as you aren't in anyone's way) and see what other compositions you can create.