Final Chapter:
To unlock the final chapter, get all Battle Masteries. Complete the final chapter to unlock two new characters for New Game Plus mode.
New Game Plus:
Complete the game to unlock New Game Plus mode. In New Game Plus mode, you can set the difficulty from 1-10, add a special item that increases stats, and retain all unused stat points from the previous game session.
Beat the game. Also, upon finishing the game, one can increase difficulty 1-10; as well as add a special item that increases stats. Unused stat points also carry over.
Recruit Mech-Hisui:
In Stage 47 of Haruna route, If Kohaku and Hisui have a combined kill count of 50, then Mech Hisui will join you.
Recruit Satsuki:
You can get her at the end of stage 29 of Takumi’s route. You have to kill her twice with Shiki. She appears in stages 5, 20 and 21.