Unlocking characters for Free/Combination/Survival Mode

Platform: Playstation 2

You have to do the following in story mode:
Asakura Saya - Find all the evidence.
Doi Junpei - Finish 1st stage in story mode.
Nakatugawa Kazuya - Examine all evidence.
Ogata Shunsaku - Finish 5th stage in story mode.
Sima Ryuji - Finish 2nd stage in story mode.
Honjo Yuichiro - Collect all the letters from all the people you can save.