You know a restaurant has got it going on when it’s nearly full on a weeknight even before 6 p.m.

Such is the case with Rantei, the Japanese restaurant located in the Franklin Square Mall in Santa Clara.

The city long ago — and perhaps foolhardily — demolished its downtown and erected this small, open-air, concrete-faced mall instead. It doesn’t exactly scream warm and fuzzy. So, when you encounter a restaurant there that’s abuzz with activity, you take notice.

Step inside and you’ll find an ample-sized sushi bar with seating, as well as tables, and even tatami rooms.

It’s definitely popular with students from nearby Santa Clara University, too, no doubt because it has a large menu, with a variety of traditional and more contemporary fare.

With four chefs behind the sushi bar, the food comes out quite quickly once you order.

With its clean, bright flavors, hamachi carpaccio ($17.95) is a wonderful way to start. Slices of raw yellowtail are strewn with sweet, sharp and crunchy raw onion slivers, radish sprouts, and citrusy ponzu sauce.

A half dozen takoyaki or octopus balls ($10.25) arrive hot, their crisp exteriors giving way to a creamy center. They’re strewn with bonito flakes and a sweet-savory, thick Japanese barbecue-like sauce, both of which up the umami level.

For a more novel creation, look no further than the fish tacos (a pair for $12.95). Tempura-fried nori takes the place of a crisp tortilla, and gets filled with seared albacore, salmon, avocado and pico de gallo. It’s smoky, a touch spicy, and vibrantly fresh tasting. It’s a little Mexican and a lot Japanese.

The tacos are big, bountiful and absolutely delicious, though, quite messy to eat. At first, you’re almost at a loss as to how to tackle them. I ended up using my chopsticks to eat a little off the top, before attempting to pick up the taco with my fingers. It shattered with the first bite, so I ended up eating the rest with chopsticks from my plate.

My husband went with the katsu don ($16.95), a generous plate heaped with a tender, sliced, fried pork cutlet and a saucy mixture of mushroom, egg, and scallion, all over rice. It’s a homey dish full of pure comfort.

It comes with miso-seaweed soup, and a green salad that was overzealously dressed with a thick, creamy miso dressing.

The omakase sashimi is one of the restaurant’s most expensive offerings at $63.95. The presentation is beautiful, with a 9-compartment bento box brought to your table, each holding a small ceramic dish of sliced fish. It’s billed as 16 pieces of fish with one mini ikura don (salmon egg rice bowl). There’s also a small serving of pickled wasabi stems.

The quality of the fish was impressive, especially the fatty salmon belly sporting hasselback-like cuts; the thick, meaty ahi; and the sweet ebi (raw shrimp).

For dessert, I had to try the Japanese waffles (2 for $6.50) when I read that it comes in the flavors of strawberry and Hokkaido milk. I’ve been a sucker for Hokkaido milk products ever since visiting Japan and falling hard for its impeccable soft serve.

The waffles are folded taco-style around the filling. They are soft and cakey, along the lines of dorayaki pancakes. Or as my husband declared, “Like Twinkies.”

The Hokkaido cream filling tasted very much like whipped cream — rich and airy, though I’m not sure it necessarily matched what I enjoyed in Japan. I actually liked the strawberry more because of its vivid berry taste.

I can’t wait to return to try some of their specialty maki rolls next time.