When I lived in Washington, DC, one of my favorite places to eat was Chipotle, the formerly McDonald’s-owned seller of giant burritos. The combination of spicy salsa, sour cream, guacamole, and seared meat all wrapped in an overstuffed tortilla made for a reasonably priced explosion of flavor, guaranteed every time.
Accordingly, a complete lack of anything comparable in Japan (or any decent Mexican food, for that matter) has been a source of considerable homesickness for me.
Joe has pointed me to Frijoles, a restaurant in Azabu Juban with a menu essentially identical to Chipotle. I have not eaten there yet, but it has so far received some positive word of mouth. I’ll be sure to report once I’ve had the chance to try it out.