When an upscale sushi restaurant transforms into a bustling hub of midnight activity (cheap eats included), there's really no better place to be on a Thursday night.

NEWJASS QUARTET THURSDAYS

Where: Sansei Seafood Restaurant & Sushi Bar in the Waikiki Beach Marriott Resort and Spa, 2552 Kalakaua Ave., 931-6286.

Hours: The band plays from 10 p.m. to 1 a.m. every Thursday.

Parking? The hotel offers valet parking for $12 — and the restaurant doesn't validate. If you're willing to walk a few blocks, try the zoo parking lot on Kapahulu Avenue.

The appeal: All the sophistication of a good restaurant, none of the pretense; all the fun of a good club, none of the pretense.

The smooth funk-infused jazz of the Newjass Quartet is the soundtrack for laid-back, feel-good socializing. Throw in Sansei's signature sushi for half price, no cover charge and a crowd that's friendly enough to mind its own business, and you've got a night worth staying up for.

Who parties on a Thursday, anyway? By the looks of it, everyone. At midnight, the moderately sized restaurant is filled to capacity with everyone from hungry late-night noshers who know a good deal when they see one ($3 for a spicy tuna roll? Of course they rush in!) to jazz heads (young and old) who know good music when they hear it, to friends of the band (rumor has it that Newjass drummer Justin James has quite the following) to hotel guests who unknowingly stumble on the activity. The result? An all-in party atmosphere that can be whatever anyone wants it to be.

What to wear: No one's telling you how to dress at this party. Feel like hitting the town in your best high-waisted jeans and off-the-shoulder blouse with buckles where the buttons should be? Knock yourself out. You may not fit in in the real world, 1982 rocker girl, but here, you're as welcome as the guy in the aloha shirt, denim shorts and loafers.

Not that Miss Modern Day in her 7 For All Mankind double-knit jeans isn't turning heads. She and that guy in the painfully hip Led Zeppelin tee obviously belong here, too ... along with everyone else.

Isn't inclusiveness awesome?

What to do when the band takes a break: When the jazz stops, you're expected to rock — and rock hard — to Kanye West's beat-driven tongue-in-cheekiness or to get down with Alicia Keys' soul-thumping vocals.

Easy, right? Smooth jazz, smooth jazz, smooth jazz ... hip-hop ... smooth jazz. It's actually easier done than said because it's really not a stretch to move from one groove to the other. If the rhythm doesn't move you ... eat.

The band: Thursday night at Sansei is Newjass Quartet's only regular gig. The guys play long sets of smooth jazz that's dirty enough to please the cool jazz fans who stand by Miles Davis, Dave Brubeck and Stan Getz, and slick enough to please the lovers of the fathers of fusion like Herbie Hancock, Tony Williams and Wayne Shorter.