Really? The difficulty is not that bad; the way to go is to abuse dash and charged dash attacks, as these make Misa intangible and teleport her a good distance. That means a) if you're being attacked it's pretty easy to warp out of range and b) if you attack using dash or charged dash, you just have to make sure you reappear outside of the enemies reach and there's zero risk.
For people having trouble:
As habisain pointed out, dashing is your best friend here. You don't need to kill everything you see unless you are doing the crystal event (e.g. the first one, 2nd one only requires you to survive for 100sec, and teaches you how to use the dash).
Additionally, equipment actually means something here.
If you are too wimpy to deal with the barbarians, equip 破毒のブレスレット to counter it
If you are getting violated by the succubus, then equip 精神のブレスレット, etc. etc.
If you are still stuck, you can try using the cheat equipment you get at the start.
The 3rd ring give you ability to use your super attack (shift key) with no cost... this is a large area AOE attack.
And if you read the readme, checking your bed 10x unlock an option that allows you to 1 hit kill all mobs.