The Four Heavenly Kings are Oda Nobunaga's generals. As the name says, that are four powerful people that could very well be the Sengoku versions of the Black Mage Generals. Currently only two of the KIngs can be fought.
Akechi Mitsuhide is a master swordsman with a very feminine like figure, and is Hayato's rival. When he is transported to Maple World, He and a number of solders defected.
Princess Nōhime. or No, is a powerful woman with her own four body guards at her disposal. Being married to Oda, this makes her a very powerful force in Oda's army. She is fought in the Hieizan Temple.
- In Chinese culture, the Four Heavenly Kings are gods who have control over the cardinal directions.
- In real life, Mitsuhide did betray Nobunaga. At Honoji (implied in the Sengoku storyline), Mitsuhide ordered his troops to storm the keep, killing Nobunaga in the process.