No, this has nothing to do with Square's popular Mana series, despite the identical Japanese title. This one was actually from Compaq - yes, they published a few games in the '80s - and like Dungeon very much inspired by the early Ultima games.
After creating your character (you can freely distribute a set amount of points between Strength, Agility, Charisma, Wisdom and Intelligence), you're dropped at this spot on an overworld map. Even getting around is a pain in the ass, though, because you have to press "M" before every single step. This is especially annoying on the laptop I'm using to play it, cause I have to switch the right part of the keyboard to turn into the numerical keypad, and "M" is inside that area, so I have to switch back and forth for every step.
Combat is weird as hell, but also somewhat interesting. Whenever you're confronted by a randomly appearing "army," you chose the number of rounds to be fought, before the opposing parties proceed to whack each other on the head. If you type "100," it's 100 rounds, if you type "1," it's just a single one, and so on. So if you fear you might lose the fight, typing a low number might be wise, but you're only getting loot if you take out the enemy entirely (which is typically 10 hits). The only problem? Even if enemies look exactly the same as others you've met before, their strength fluctuates wildly. Oddly, the game doesn't quit when you lose all your hit points, but you're stuck in the next fight, cause you cannot type in "0," but also no more than the amount of your hit points.
I don't know if this game has a dungeon, but it does have towns and castles, which fit on a single screen, like in the very first Ultima.
In the towns you can of course get equipped. It seems every weapons and armor you buy is equipped automatically, but I don't know if they accumulate... "Trans" is for transportation, and you can buy a bicycle, a horse, a boat, a coach, a car, a ship and a magic carpet. At the "Store" you get matches, water tanks, fishing gear and tents. The weirdest thing: Once you selected "buy" to see the wares, you can't seem to back out of the purchase again. As the other shop suggests, you consume food, but the game is rather generous with it. You start with 100 units, and it takes a long time before those are used up. I never managed to do anything at the pub.
In the castle you can visit the king - if you know the password, which I don't. Moving on...
Crossing the river on my boat. The boat disappears after one use.
South of the river I've encountered these guys, but otherwise everything looks the same.
"I'm a witch. I've put the princess to sleep with my magic. The Way to open the white door is *Kasumaeramoterei*
This guy requires an "action spell," which of course I don't know. It's white, but it doesn't look like a door...
When wandering around the map, one eventually meets this guy, who appears again and again. He has some kind of riddle: "A clock that's 7 minutes late has shown 7 O'clock 7 minutes ago." But I couldn't type in the correct answer, cause the key of a necessary character (the "-like thing that turns consonants softer, like t into d or s into z) apparently isn't mapped on my keyboard.