Bonus costumes
During or after Chapter 7, select Leanne, and look at the wardrobe in her room. When she says "Hmm, I think that outfit is in here...", enter one of the following codes, then press A to advance to the next line of dialogue and unlock the corresponding costume:
8-bit Girl: Press Up(2), Down(2), Left, Right, Left, Right, Triangle, Square.
Club Famitsu: Press Triangle(2), Up(2), Square(2), Left(2), L1, R1.
Gemaga: Press R2, L2, L1, R1, Triangle(3), Square(2), Up.
Hirakou: Press Square, Triangle, L1(2), R1(2), L3(2), Up, Down.
Platform Logo: Press Left, Up, Right, Down, R1(2), L1(2), L3.
Politan Suit: Press R3(3), Right, Left, Triangle, Square, L2, R2, L1. Note: You must get the Reindeer Suit in Neverland first.
New Game +
Successfully complete the game. You can now start another playthrough with your saved game file. Additionally, in Chapter 2, you can enter ReanBell's (Leanne's) bedroom and press [Action] at her wardrobe to activate a secret button. It allows Reanbell to remain in her current costume instead of changing into the pig t-shirt in the cutscene.
Easy money
In Chapter 6 or later, the Combat Scope Betas cost 3,000 gold, one glass shard, and one scrap of iron to make. The wandering merchant sells glass shards for 200 gold and iron scraps for 150 gold. Combat Scope Betas sell for 4,100 gold. Thus, you will make a profit of 750 gold per scope. The best time to do this is chapter 6-7, before the merchant starts wandering she is always at the Waterless Bridge. In Chapter 8+, she can be at Forsaken, the Waterless Bridge, or the Righteous Tower. It is recommended to get into an enemy counter, run away, and check the location to see if she is there. Time phase changes also alter her position. Repeat this trick as many times as desired.