ISO file structure is:
.
├── PSP_GAME
│ ├── ICON0.PNG
│ ├── PARAM.SFO
│ ├── PIC1.PNG
│ ├── SYSDIR
│ │ ├── BOOT.BIN
│ │ ├── EBOOT.BIN
│ │ ├── OPNSSMP.BIN
│ │ └── UPDATE
│ │ ├── DATA.BIN
│ │ ├── EBOOT.BIN
│ │ └── PARAM.SFO
│ └── USRDIR
│ ├── DATA.DAT
│ ├── STS.DAT
│ ├── STS.MAO
│ ├── STS_DEF.TOB
│ ├── modules
│ │ ├── libpsmfplayer.prx
│ │ └── psmf.prx
│ └── movie
│ ├── IF_logo.pmf
│ ├── ending.pmf
│ ├── opening.pmf
│ └── otomeito_logo.pmf
└── UMD_DATA.BIN
DATA.DAT's header is "PSPFS_V1", it can be unpacked by this quickbms script
# ClaDun X2 (DAT format) PSP / PC
#
# Written by Ekey (h4x0r)
# http://www.progamercity.net
#
# script for QuickBMS http://quickbms.aluigi.org
idstring "PSPFS_V1"
get FILES long
get NULL long
for i = 0 < FILES
getdstring NAME 0x18
get SIZE long
get OFFSET long
log NAME OFFSET SIZE
next i
There are a bunch of files and no directories. Here's file list.
*.VAG files are "Sony ADPCM 4 bit" files with voice data, this is a known format which can be decoded by several tools ([1] for example).
*.DAT files are gzip-compressed with 0xC extra bytes prepended. After removing this extra data they can be extracted with gunzip or any other tool.
_EXFONT.DAT: gzip compressed data, was "_gz_div.tmp", from NTFS filesystem (NT), last modified: Thu Feb 3 08:27:52 2011, max speed
The original file has "DSARC FL" header. This format seems to be known as well ([2], pages 201-202) although I personally didn't try to extract it. They probably contain .MBP files.
Sadly, I have no idea about .SP2 and .MBP, I've uploaded them here.