It depends. If it is luxurious, it must be expensive. However, there are luxury shopping malls in Tokyo with relatively affordable prices for luxury brands.
That's certainly a comfortable budget as long as you aren't expecting to eat many fancy meals or do a lot of drinking or clubbing. You can probably save some money with strategic use of transit passes (see summaries on Japan Guide or elsewhere). You should look into the Grutto Pass.
The cost of food in Japan can vary depending on the type of food, location, and restaurant. In general, dining out and grocery shopping can be more expensive in Japan compared to other countries, due to the high cost of imported ingredients and limited land availability for domestic agriculture.
100,000 yen should be sufficient, excluding your accommodations, transportations and theme park admissions, unless you're expecting to buy an expensive souvenir. I would carry a credit card for peace of mind.