Back side start
On the title screen, press [Right, Down, Up, Left, Right, A, B, Start] to start the back side. If the MAP color is brown as shown in the image below, it is successful. If you press the wrong command even once, subsequent inputs will be rejected, so if you fail, reset and try again.It starts from ROUND 13 and is cleared on ROUND 24 (front side is 1-12). Even if I earn EXP, my maximum vitality does not increase and the enemies become stronger. Furthermore, the item placement is different, making it difficult to obtain valuable items such as swords. The clothes of the rescued maids and princesses change to swimsuits.

How to dash
Dashing is done by hitting twice in the direction you're heading, but you can also dash to the right by quickly pressing left and right.Expansion of items
If you acquire the same item three times in a row, the number of items you own will increase by +10. (1 piece → 2 pieces → 12 pieces)However, instant items and equipment such as swords are invalid. Applies only to magic items such as scrolls, rods, lamps, rings, amulets, chalices, and crowns.
Summary of what we learned from the analysis (small notes)
Uninvestigated items