Don Quijote, aka Donki, is a well-known discount chain store in Japan, and it's been featured in the Yakuza series since its first release (and it's been selling the games since the second installment). Think Pikachu onesies, rice cookers, bikes, headphones, matcha-flavored Kit-Kats and sex toys, all in one place. Part of the store layout here in the game was surprisingly similar to what I saw in real life, though the game only offers one floor to explore. The Yakuza series isn't the only game franchise to replicate Tokyo in detail: Persona 5 somehow managed to recreate the chaos of Shibuya, train station and all, faithfully. It didn't, however, have the brand clout that Yakuza apparently wields.
Real Japanese eateries such as Sushi Zanmai and Cafe Pronto are dotted around the game as well, though you might not find them at the same locations in the real world. Kiryu can also get a membership at fitness chain Rizap in order to boost his various stats -- and gets his own before-and-after montage in the process.
It's also worth pointing out that you can buy items that exist in real life, mainly beverages (Suntory has also been a longtime collaborator since the first release) and medicines. Kiryu even uses a Sony Xperia XZ, which is a nice upgrade from his old feature phone -- at least he can take selfies now.