Disk Union is the place I hit when I go to Tokyo. They have shops all over. I usually stay at Sunroute Plaza which is walking distance from Shinjuku Station. U will find a cluster of Disk Union shops nearby. They have a branch selling hifi there too. What I like abt Disk Union is that their records are organised well. At Shinjuku, Shibuya and Ochanomizu, u will find shops that have different genre of music in different floors. Ok last visit was in 2019 so not sure if there's any changes. Oh gosh I'm on heat now 😅