No spoilers, but I knew even before I’d reached for my chopsticks that Mitsu would be a vast improvement on its predecessor, because it has taken the place of Nobu Shoreditch in the under-gusset of the Aethos hotel, a Swiss-owned “lifestyle hospitality brand”, in east London. Nobu was gargantuan, moodily lit (that is, pitch black), woundingly expensive and terrifically hard to book, despite having something like 797 seats; it was also one of the most soulless London restaurants of the past 25 years. Nobu Shoreditch felt symbolic: it was where all the raffish hope of the 1990s YBA crowd and the early noughties electroclash heads went to die.

But that was then, and now, in 2026, the Aethos crew has deftly brightened and lightened the mood of the room, making it actually cosy and adding a twinkly central bar; there’s an open robata kitchen and roomy booths, as well as a pretty Japanese garden. Mitsu calls itself an izakaya, which is what European restaurateurs always say when they mean the Japanese-influenced food isn’t too po-faced and you can get really tipsy on sake.

Not that the place isn’t serious about its sushi and sashimi – there’s plenty of good unagi, hamachi, chutoro and so on – but there are also a lot of tasty little snacky things, such as very good chicken tsukune (meatball) skewers to dip into sweet tare sauce and two Shoreditch-requisite sandos: pork belly with mustard and wagyu with tonkatsu sauce, both in rich, milky shokupan. From the robata, you can have a porterhouse steak with sansho pepper sauce or a pork tomahawk with kanzuri miso.

Leading the kitchen is Aaj Fernando, ex of La Bodega Negra, which back in 2012 was a mega-hot, secret Soho restaurant under a fake sex shop, which was also impossible to book. It’s still there, apparently, although these days no one seems to care about it much, least of all Fernando, who is now out east and busy feeding a new set of subterranean bright young things.

I abstemiously order a green tea, because my days of dancing on tables in this postcode are long behind me. If they weren’t, I’d have ordered a whisky highball – two, probably – or some of the £4-a-glass sake from the Kanpai brewery down the road in London Bridge. I wasn’t in the mood for miso soup, edamame or tsukemono (house pickled veg), so I passed on the snacks section and dived straight into the kozara (small plates), where chicken and squid karaage sit beside pork gyoza and seafood dumplings. I ordered hamachi (yellowtail), which came in a pool of katsu ponzu and dotted with a silky, earthy cauliflower puree that, rather than being overpowering, was just right.

The staging of the wagyu sando, however, struck me as a bit rustic, cut into four chubby sections, crossways like a toddler’s post-Pigeon Street lunch. The steak itself was thick but tender, while the bread, like all shokupan, was sweet, rich and impossible to stop eating; it may as well have been madeira cake. Japanese-influenced sandos often have about them a death-row dinner aspect, not least because each gorgeous bite takes you merrily closer to the grave.

Mitsu won’t win any plaudits from Japanese purists, who will turn up their noses at the grilled beef fillet with garlic and soy butter and the soy-glazed salmon skewers – they shouldn’t fret too much, though: at least they draw the line at chips. And they definitely won’t want a whopping portion of matcha tiramisu scooped from a big bowl tableside in a cool Insta moment, although that’s exactly what much modern dining requires, especially round these parts.

Still, this is a determinedly fun and delicious place to have up your sleeve. The chutoro sashimi was genuinely excellent – fresh, fatty, supple, devourable – and special mention should also go to the akami temaki – delicate, crisp nori boats filled with rice and lush red tuna; those juicy chicken meatballs, too, are worth the trip alone.

There’s a sense here, though, that Mitsu is delicately balancing its urge to attract Shoreditch’s new content-creating crowd (sandos, slopped-out pudding) as well as an older, moneyed clientele who want actual sashimi and sake. It’s not remotely earth-changing, but it is a large, warm space with great staff, and I’d happily pop by again for a solo lunch. Businessy groups will appreciate the bigger booths, while friends and couples can chat happily because the soundproofing is brilliant. The menu, meanwhile, lends itself more to scoffing a little too much than to picking solemnly at a tiny piece of expensive fish and congratulating yourself on clean eating. So farewell, Nobu, I won’t miss your black cod and lack of light bulbs. I like Mitsu much better.

• Mitsu 10-50 Willow Street, London EC2, 0287 114 0040. Open all week, lunch noon-4pm, dinner 5pm-midnight (1am Thurs-Sat). From about £80 a head à la carte (set menus at £85 and £105), all plus drinks and service