When I first started fishing for them it was often a bit of a struggle, most people were swinging small streamers. It did work, but didn't really feel like the catch rate was in keeping with the numbers of fish. It's actually not that unusual to see Japanese "anglers" actually trying to snag them rather than catch them cleanly - horrible. Luckily someone figured out that nymphing is incredibly effective for maruta and as word gets out the snagging is fading out.
As covid means I won't be spending my spring holiday in the jungle with Paul, last week I went to the Tama river which runs between Tokyo and Kawasaki, I was really planning to fish for smallmouth and walk the river to see if there were any maruta in the system yet. I started well with a nice chunky pre-spawn smallie in pristine condition and full of ayu. Surprisingly I only had to walk a couple of hundred metres to find a big school of maruta much further upstream than I expected them to be. I switched to a tungsten beaded squirmy worm and got stuck in. It didn't take long to catch a handful and lose another couple before I got a bit bored and decided to leave them and scout more of the river. The efficacy of nymphing is a double edged sword, it's too easy when the fish are stacked up in numbers. Much better to find them in small pods where there's less of competition factor among the fish. You'll catch fewer, but it won't get boring because there's a challenge and you have to fish well to get them.
In normal circumstances this is the most popular season for visiting Japan, so if you ever come here for the cherry blossom parties, why not stick a 6 weight and box of nymphs in your case and take advantage of this uniquely Japanese fishing opportunity.