I'm quite a big fan of old games that were never released outside of Japan originally but that have made it over to Western shores many years later, and so I was interested in trying out the Nintendo Switch Online Famicom title Ninja JaJaMaru-kun (the last game I played in this category was the quite enjoyable if not particularly surprising Mario's Super Picross). The game was originally released outside of Japan on the Wii Virtual Console, but it should have a wider audience on Nintendo Switch Online.
Ninja JaJaMaru-kun is definitely an old school arcade game and of its time, meaning that it's pretty simplistic by modern standards in terms of its mechanics, presentation, and progression. The game reminds me a bit of Ice Climbers in that you can break blocks to move between four different floors, although in this game your goal isn't to reach the top of a mountain. Instead you're just tasked with defeating every enemy in the stage. The game features similarly stiff jumping controls, which definitely adds to the challenge. Every stage has eight enemies, one of which is the more difficult one, and every few stages the eight enemies shift so that seven of them are the previous stages' difficult enemy and a new, more difficult enemy is introduced, which is a novel game mechanic. To defeat enemies you can throw shuriken or jump on them to stun them. In earlier stages you can get by with just using your shuriken, but in later stages the harder enemies require that you jump on them first.
As with the original Mario Bros. game, you can also earn bonus points by collecting the spirits of the enemies you defeat, which float up from where you defeated them. You also earn bonus points from the petals that your love interest drops from the top of the screen, while also having to avoid bombs that your enemy drops. Lastly, there are also bonus items (and occasional hazards) hidden in the blocks you can break. Many of these just add to your score or are only marginally useful, but these bonus items tie into the best feature by far in the game. If you collect three different types, a huge frog jumps in to help you out, and you go into this sort of rampage mode where you can hop around the stage on the back of the huge frog and gobble up any remaining enemies in the stage. It's as awesome as it sounds, trust me. There are also time bonuses as well for beating a stage quickly.
Ninja JaJaMaru-kun does have that old-school difficulty and repetitiveness, but infinite save states and rewind features make it much easier to work your way through the game's 22 unique stages. I wouldn't say that this is an essential game, but it's on par with many of the other Nintendo classics that, from a modern perspective, are similarly awkward and difficult. Apparently the game was a big success for its time, and Wikipedia says that "sold nearly 1 million units, becoming one of the best-selling Famicom games". It looks like there were quite a few sequels, but from what I've seen of them online, I'm not sure they really improved on the charm and simple but fun arcade action of the original. I doubt I'll be coming back to this one any time soon, but it was fun to try it out, and I'm always happy to see previously unlocalized old school games make an appearance in other regions many years later.