Knights of Valour - The Seven Spirits

-Unlock Dubhe-
After the game has been running for a certain amount of time, Dubhe's icon will appear on the title screen. Once that happens, go to the character select screen, and place the cursor on the following characters to enter the code. Once entered, Dubhe will appear in the middle of the screen.

Japanese Version:
Place cursor in Mizar (2nd character from the right), press Up, Up, Down, Down, then hold Start and press B, C, C, A, A, B.

Simplified Chinese Version:
Place cursor in Mizar (2nd character from the right), press Up, Down, Down, Up, then hold Start and press C, A, A, B, B, C.

Traditional Chinese Version:
Place cursor in Alioth (2nd character from the left), press Down, Up, Up, Down, then hold Start and press A, B, B, C, C, A.

North American Version:
Place cursor in Alioth, press Down, Down, Up, Up, then hold Start and press A, A, B, B, C, C.

-Reach the true last boss-
To reach the true last boss, you must fulfill several conditions. First, you must accept Chapter 4 and get the Scarlet Finch from the boss. I've gotten it by simply hitting the boss.
Second, the chapter 7 boss is random and you'll face either Liubei, Caocao, or Sunquan. After defeating that boss, you'll go to a second phase. For Liubei, you must defeat the white tiger (Lan) in 30 seconds or less and he'll drop the Ashy Tiger item. For Caocao, defeat Onyx Cao in 40 seconds of less the and he'll drop the Snaketortoise item. For Sunquan, perform a 22-hit combo on Cyan Quan and he'll drop the Cyan Dragon item. Third, you must have over 1,500,000 points after beating the last boss in Chapter 8. To get that many points, you have to learn advanced combos to get as many points as possible from defeating enemies, you also need to pick the best level routes, and successfully save villagers when prompted. If everything was done correctly, you'll get energy recovery items when you defeat Dubhe and you'll proceed to the true last boss.
If you're playing with the secret character, there is no Chapter 8 and instead you'll go from Chapter 7 to the true last boss if you fulfilled all the conditions.