This game's also known as Youkai Yashiki and Haunted House. I have no idea where the "Haunted Boynight" name comes from, but that's what it's called in many romsets, and it's a lot more eyecatching than the other, probably more legitimate titles, so that's the one I'll use. It's a surprisingly complicated and ambitious platform game that's not quite a search action game, but a little more complex than a traditional platformer.
You play as a boy, going into a haunted house to save your sister, who is apparently a renowned paranormal investigator who went missing there. (At least, that's what a comment on a Youtube playthrough says the plot is, anyway. That video and its comments being pretty much the only source of useful information on this game that I've been able to find). Your only weapon is a flashlight, which damages ghosts when its light hits them, and that's where the first really weird thing comes in. When you start the game, your flashlight is a melee weapon, but if you use it to dispell the wisps in the garden leading up to the house, it'll start shooting a projectile, until you get hit. This also does something to make you stay alive longer, but the way your health and lives work in this game is enough of a mystery that I never fully worked it out.
The basic goal of each area is pretty simple: find five paper talismans, whih will then turn into a key that'll allow you into the room where the boss is. You have to find the boss room yourself, of course, and as the game goes on, the stages get bigger and more byzantine in their layout. Therer does tend to be more than five talismans in each stage, though, and your surplus get carried over. In fact, I'm pretty sure that the game is actually a big open world, with more areas getting made accessible with every boss defeat. I'm not totally sure, though, as the only time I went back to a previous stage was by accident. Because there are what look like stone firepits dotted around all the stages, and when the fire's not shooting out of the top of them, you can stand there and press down to get taken away to somewhere else that might be hell or might just be a network of caves under the house? And there are also firepits down ther that'll take you back to the house, not necesserily in the same place you left it, though.
Another thing that won't be immediately obvious are the little monk statues standing around in certain places. If you touch them while carrying a rice ball and a depowered flashlight, they'll take the riceball and repower your flashlight. But they also have a second function! Stand in front of them and press down, and a small part of the wall or floor nearby will disappear, opening a new path. This is actually necessary to get into one of the boss rooms! The bosses themselves are the most mysterious of all. They all have one very specific weak point that's not at all obvious, and I only figured out most of them for the four bosses I fought by watching the aforementioned playthrough video. Sometimes the weak point is easy to rerach, and needs to be hit a bunch of times, sometimes it's hard to reach and only needs to be hit once. But again, in almost all cases, it's not something you're likely to figure out on your own. I wonder if all these "secret" things were listed in the manual, or if this is a game that just wanted to extend its playtime through obtusity?
To be honest, this isn't a great game. Like I've described, it's mostly about figuring stuff out either through luck or through looking it up online. The first stage does do a good job of creating a ver Japanese haunted house atmosphere, but it's unfortunately a case of severe frontloading, and the following stages just feel like some generic 8-bit microcomputer platformer world. This isn't one you should seek out and play yourself. Maybe just play through the first stage, for the atmosphere, but don't bother going any further.