The demo for this one alone already has multiple times as much content as the entire first game, so I'm pretty damn stoked for that.
I don't know if anyone's noticed yet but enemies have an in-combat rape animation (for some enemies it's the same as their game over animation, for other's it's different). You can tell the attack is coming because once you get their health below a certain threshold, a pink bar will start filling up underneath their health bar (it fills gradually over time + it fills faster when the monster deals or takes damage.) When the bar is filled, it'll fire a grab attack that does a fat chunk of upfront damage and starts a rape animation, which, while it doesn't do any extra damage, will increase your arousal. If you cum, you lose a chunk of health and get stunned for a very long time. If the rape animation plays all the way to the end, you also get stunned for a duration based on how aroused you are.
Difficulty is a little steep, but grinding isn't that hard once you realize you can skip scenes you've already watched by pressing A. EXP gained is based on the amount of damage you dealt, so if you want to level up fast, unload all your mana doing as much damage as you can, then just beat the enemy up until it kills you and skip the game over scene.
Combos in this one handle a little differently than in the first game. In the first game all you had to do was hold the attack button to execute the combo, and while that does still work here, it's not the efficient way to do it. Instead, there's a timing system where if you press the attack button exactly once right as a hit connects, you'll follow up with a stronger hit in the combo, leading up to a multi-hit attack and finally a huge, heavy downsmash. The combo timing is tricky to learn and even harder to keep doing when the enemies keep moving in and out of range (the combo drops on a miss) but if you can keep the combo going you can stunlock single targets and deal absurd amounts of damage.
Also, I think it's unintentional, but if you get to ng+'s first enemy encounter (the one that comes after the slime boss) it's a dual fight against the flying rectanglemaru thing (the first enemy you see after the worm) and any random enemy from the entire game. If you keep losing and retrying, eventually you'll encounter enemies that very clearly aren't supposed to be in the demo. There's a lot of them to encounter, most of them have in-combat grapples already implemented (though one or two will softlock the game if you let the animation finish) and this all says to me that there is a TON more to come in the full game. I'm really hyped.
I believe there are going to be special game overs for each enemy and trap you can encounter in exploration mode, but the demo doesn't have them (I think that's what the message you get when KO'ing in the lower floors means, anyways) and there's already a good variety of traps, which more having been previously teased on the dev's ci-en.
Final note: because this is a demo, you aren't allowed to save. You're not missing something, you just aren't allowed to save, straight-up.