To Heart 2: Dungeon Travelers is due out later this month in Japan, but Aquaplus have a demo version of the game for PSP owners to try out while they wait. You can find this here. Click the blue button on the right (at the bottom) to proceed until you find the big red button that lets you grab the demo.
The Dungeon Travelers demo allows you to level characters up to level 10. To Heart 2 also has a class change system, but unfortunately, you won’t be able to try this out in the demo. However, on the bright side, your data will carry over into the full game.
To Heart 2: Dungeon Travelers is on track for a June 30th release. People that buy the limited version for for 11,340 yen ($140) will get Tamaki and Konomi nendoroids with it.