Lol, sorry :s
Well, I’m testing it right now. And indeed, mp3 files play as intended 
Unfortunately… the step5 issue is still present… but still loads if launched cfw first (start cfw, open yellows8’s homebrew launcher loader, launch EasyRPG and it works). Plus, cia version works as intended too, and I expect the built-in cias to be that way too. So for now, I guess you can say that EasyRPG on 3DS is cfw-only…
Btw I did something I consider necessary: I made a (small) list of games you can and can’t use as target app when launching EasyRPG through HBL normally, despite being useless right now. I’m posting it in Rinnegatamante’s forum too:
This list may not be 100% accurate since except for Mario Kart 7 and the Lego Harry Potter game, the other games were tested using a Sky3DS I own instead of the retail cartridge which I don’t own. Also none of the default system apps work as target app (at least for me), if trying to set them, the top screen will get stuck with the keyboard that is expected to be shown in the bottom screen, but all meesed up and rotated 90º to the left, and the bottom screen will get stuck in red. Finally, I did the test on my 9.2.0 sysnand, I guess it may vary if you try in another console with a different firmware version (I think the list would become shorter, but who knows…). All right, let’s begin:
Working game target list:
-Mario Kart 7
-Super Smash Bros. for 3DS
-Mario and Luigi Dream Team
-Paper Mario Sticker Star (Seems to crash, but it actually loads…)
-Mario Party Island Tour (Same as PMSS)
-Yoshi’s New Island
-Tomodachi Life
Not working game target list:
-Lego Harry Potter Years 5-7 (gets stuck like default apps)
-Cubic Ninja w/ninjhax (stops with blue bottom screen, didn’t try without having the exploit installed despite it doesn’t work anymore…)
-The Legend of Zelda Ocarina of Time 3D (couple of junk bars appear randomly on the top screen and bottom screen remains red, but won’t go farther than that)
-Super Mario 3D Land (gets stuck like default apps)
-Mario Tennis Open (gets stuck like OoT3D)
-Ultimate NES Remix (gets stuck like default apps)
-Tetris Ultimate (gets stuck like OoT3D)
-Boulder Dash 3D XL (gets stuck like Cubic Ninja)
-Freakyforms Deluxe (gets stuck on red bottom screen displaying nothing on the top one. Yup, people using freaky hax won’t be able to use it… for some reason…)
-Senran Kagura 2 Deep Crimson (gets stuck like OoT3D)
-Out of region games (get stuck like FreakyForms)
Well, that’s it for now