Izuna: Legend of the Unemployed Ninja Cheats on DS

Continuous weapon power-up

Once you get to the Fire God's dungeon, you can continue to upgrade your weapons without stopping. Simply fight inside the Fire God's dungeon and find several burn-in orbs. Fill up your weapon with Zoufuku Talismans (increases the SP capacity of your weapon; the Zantetsu sword that ignores defense is recommended), then burn them in with the burn-in flame. Your increased SP capacity will remain on the weapon. After that, keep filling your sword with Rekka for attack, Mikagami for defense, Kaishin for critical hits, and Mikiri for evasion. Keep burning them in and switching to Zoufuku for more SP, and your sword will have very good stats by the time you finish. Make sure to keep an un-burned Kikan talisman stuck to it, just in case you actually are defeated.

Bonus dungeons

Complete the main story line to unlock the following dungeons.

Girls Only Dungeon located at the shrine near Himiko
Mugen Chasm located where Shizune ran to.
No Item Dungeon located at Surei Town. The Gankatsu talisman is required.

Bonus characters

Complete the main story line, then talk to the following bonus characters at the indicated locations.

Gen-An
Himiko at Kamairi Village
Hinagiku at Mugen City
Ichika at Surei Town. You must first unlock the No Item dungeon.
Suzuri at Kamairi Village