Since I haven't yet been able to convince you that opening a restaurant or bar is a bad idea, the next step is to start asking you questions. What is your vision for the shop? What do you plan to serve? Are you going to provide something new? Are you sure there's a market for that new thing? Are you going to give people more of something that's already out there? If so, what is it that you're going to do to stand out? How, for example, is your Italian restaurant going to bring in customers in a city like Tokyo, which seems like it has thousands of Italian restaurants? And most importantly, can you keep your restaurant open with the prices you charge?
Opening a restaurant that sells something commonly available has one good thing going for it: You know there's a demand out there. But just because there's demand, that doesn't mean you'll be successful. If you're trying to open a French restaurant in Tokyo, you'll be facing educated customers who have strong expectations, and your food will need to match them.
However, if you're selling something new, you need to be sure that it's not something the market has already rejected. When we had our shop in Aoyama, some of our regular customers asked us about having brunch options available on weekends. They talked about how they couldn't find anything decent for brunch, and they thought we would make a killing by offering a small brunch menu on weekends. We thought about it, and gave it a try, but we never sold more than one or two brunch orders a day. We'd promoted the menu as best we could, but we ran into a cultural issue: most Japanese people, if they eat breakfast, eat it at home. As often as expats in Tokyo bemoan the lack of breakfast restaurants, the fact remains that if the market would support brunch, more restaurants would offer it. We were lucky that we only lost a small amount on our ill-conceived brunch venture.