It's quite a leap from the security of a long-term job at Crown to a self-funded storefront restaurant in Port Melbourne, but that's the transition Jimsan (Martin) Kim has made. After working as the sushi chef at Koko in the casino for the past 12 years, Kim decided he wanted his own business – an omakase sushi restaurant, serving only a few customers per evening.

He researched different neighbourhoods, looking into the availability of good sushi (plenty in the CBD), plus the economic demographics of different areas, and settled on Port Melbourne. And in early August, he opened the door to Asoko, the project he sees as the culmination of 20 years working in high-end Japanese restaurants.

Asoko is a spare room, decorated mainly by bottles of sake lining the walls and a forest of bamboo in the window. There are a few tables, but for now those are going unused – up to 10 customers, who arrive at 6pm for the nightly seating, sit around the sushi bar.

Kim, who is originally from Korea, oversees a couple of chefs while also acting as host and server. Because the number of customers is so limited (there were only five people dining during my visit), the tenor of a meal here is friendly and intimate.

I've had incredible sushi at similar omakase restaurants in Japan and the US where the atmosphere was somewhere between church and military camp: you revered the chef and the food; you followed orders. Here the feeling is far more convivial, with Kim striking up conversation with guests and excitedly explaining the menu and his hopes for his restaurant. "I want this to be an entry-level omakase, in terms of price," he told us, "but amazing value in terms of quality."

At $140 per person, that may seem like a stretch. But when you look at similar experiences in Melbourne (and beyond), you get his point: Minamishima is $265 per person; Warabi, the excellent new omakase restaurant in the W Hotel, is $245.

Those places are far slicker than the experience at Asoko, but I'm not sure that factor makes them inherently better. This is a more human experience – a chef/owner/operator inviting you into his space, serving you water and drinks, and operating with a true sense of welcome.

Dinner begins with an appetiser plate that holds raw and cooked slices of wagyu, an oyster topped with ponzu, lightly cured salmon, and a small dish of spinach. Next comes the sashimi of the evening: slices of buttery kingfish, firm snapper, and a roll made of minced tuna with no rice, served with freshly grated wasabi. Each dish is passed over the counter by the chefs and explained in detail.

The main event of the evening is a parade of nigiri, placed on the counter as each piece is made. The fish itself is exceptional – I'll get to that in a moment – but the thing that struck me most was the quality and care taken with the rice.

Lightly vinegared and barely warm, each grain distinct but sticky enough to hold together, this is rice made by people who really care about rice. Ever heard about how sushi chefs spend years just learning how to make rice, and wondered how that could be? Go to Asoko and you'll get some idea of the difference.

But the fish is worthy of adoration, too, particularly the varieties not often seen on Australian sushi menus. Raw duckfish, lightly brushed with soy, was opalescent and firm and fantastic. A fat raw scallop, served over rice on a strip of nori like a tiny taco, was perhaps the sweetest, richest scallop I've ever had.

A paradise prawn is served barely cooked to bring out its best qualities, and later the head comes in a small bowl of deeply flavoured miso soup. A small salad of raw fish, cucumber and tomatoes is served in the middle of the parade of sushi to act as palate cleanser between fresher and oilier fish varieties. This is a menu presented with extreme skill and a perfectionist's level of detail.

What is undeniably better at the slicker joints in town is the quality and variety of drinks served. Asoko has a sake list with a couple of interesting finds, and a short wine and beer list that is as standard as they come – big producers, not a lot geared towards the food.

And dessert seems a little perfunctory, a small nub of tempura fried ice-cream served with fruit that is neither unpleasant nor interesting – it seems like it's there because Kim felt there should be dessert. He's probably right, and I'm not sure what I'd have preferred after such an incredible meal full of freshness.

After we paid our bill and went to leave, Kim reminded us that it's early days for Asoko. "We are just getting started," he said. "We are only going to get better and better." I'd put money on him being right.

Vibe Simple small room, jazz on the speakers

Go-to dish Nigiri sushi

Drinks Sake, wine, beer, Japanese whisky

Cost Dinner for two $280 plus drinks