(Hard without knowing Japanese)
This game is very in depth there seems to be many paths and tutorials that are vital.
I found myself stuck at a point where you need to gather certain clothing items.
Sadly the clothes rip so,there must be some special way to get them.
I turned to the internet for help but, it seems that the help provided is very vauge.
Most tell you what you need to do but, not how it's done.

There is a full wiki that you can translate with Google though.
So if anyone can get past that point I'm sure it would be easy enough with the help of the wiki.

Over all I suggest either using the wiki or waiting to see if someone patches the original.
It's possible considered the 2nd game came out in the US!
In addition, here are some helpful links if you're stuck and can't find your way in game.

Short Walkthrough
Akiba'Strip Wiki
Just run this through google translate.

(Easy has a lot of symbols)
So far about an hour into the game there is symbols for everything that show you what's important.
It almost seems like this game was meant for a younger audience or, a casual type of gamer.
The style is cute so that's most likey the case. I would say if you're looking for something hardcore this isn't it.
It's very simple and easy to follow though if you're an anime fan you might love this game. I do.

The only downfall really is that there's an interesting cross over story going on.
And you won't be able to understand what exactly it is.
Another great thing is things that recover HP Items are marked with HP.

After finishing a few chapters of this game it's clear to be you can play it without knowing Japanese.
Literally it holds your hand it would most likely be a great entry level for someone actually learning Japanese.
The only bad thing is there is no online help for the game other than what's on gamefaq.
So if you start the game be prepared to do a little bit of work to figure out some things.
Still it shouldn't ever be too hard.

Gamefaqs

(Easy has enough basic English to follow the game)
While there is an English version for the Wii of Pop N' Music, don't bother.
The PSP versions of the game that were only released in Japan are much more fun.
They aren't for someone at a beginner level but, with some practice are a blast.

There is a big difference in the PSP versions.
The port to the US or EU was dumbed down for a more child friendly setting.
And the Psp versions are very challenging.
I have a feeling any DDR or OSU fan will love these games.
The colors are bright and there are a lot of songs from popular anime too!
One I noticed was the Evangelion OP Cruel Angel's Thesis.
Like DDR I believe it's a cover but, the cover is just as good as the original.

Now my guess is if you get confused you could look up a tutorial on youtube.
Otherwise the tutorial in the game isn't too hard to follow but, the beats take a bit to get use to.
But, if want to play with more buttons than easy mode I suggest doing some research.
There's no online walkthrough or faq and the Wii version plays very different.
But, it's just a rhythm game! All you really need to know is what buttons are where.

If you do find yourself lost here's a link to the gamefaq board for the first game.
You can easily find the second game from there as well.
Gamefaqs