Located in, of all places, a Days Inn hotel in Hayes Valley, this unprepossessing little restaurant doesn't look like much: five small tables crammed into a tiny circular building, with a cadre of cool young Caucasians in the kitchen and a tiny sake lounge upstairs. But just one bite of Gerard Dumuk's impeccable fish clues in the wary that this place is something special. We're haunted by Dumuk's Martha Roll, an ethereal combination of crab, mango, and mint that leaves a memory that long outlasts the cooling aftertaste. First-time visitors would be wise to take Midori up on its popular regular menu item, the Sushi Submissive, which requires patrons to sit down, shut up, and be fed according to the chef's whims. Your server may return with a classic Spicy Tuna Roll, some ultra-fresh unagi, or something you've never eaten or even heard of before. Relax. Take a bite. Dumuk knows what he's doing; all you need to do is open wide.