Resume at last level
From the menu select "Continue" and then "From Logbook Entry" and enter:
8#4V7 LprBy 4v52B j@7-T YM?0P 7/4By ;
as your logbook to start on the last level with full health, a weapon at level three, all items, and all jutsus. From here, simply keep heading up and left through the hallways until you get to a cell with a white wall. Hit different parts of the wall until you hear a sound like you're making contact. Keep hitting that spot and a door will open up. Enter and you're on the last side-scrolling mission stocked to the gills.
Resume at penultimate level
From the menu select "Continue" and then "From Logbook Entry" and enter:
¢63>¥ :tH!8 d%w!L 1G¥4M dTH6Q ¥>HLw W
as your logbook to start on the second to last level with full health, a weapon at level three, all items, and all jutsus. From here, keep heading up and go through the doors to the castle. You'll meet the king who will tell you to go find the secret passage. Exit, go down one screen, go left until you see three statues. Beat the middle one until it breaks. Enter and you're on the second to last side-scrolling mission stocked to the gills. (Because there's no 'heart' nor 'triangle' character on my keyboard, I've used ¢ to mean 'heart' and ¥ to mean 'triangle'. Make the appropriate substitutions when entering the code.)
Unlimited Hamburgers
Enter: v, x, Z, +, +, I, h, :, @, Y, n, n, 3, +, !, $, T, +, K, K, h, G, :, !, <, +, !, +, X, @, r
Level passwords...