Daigouin Jaki and Zeus's rivalry is put into a new context when you consider that Jaki literally has the Kanji for devil in his name, while Zeus is named after a chief god and also has the kanji for Holy in his name. Also, their battles are the opposites of eachother, given that Momotaro's fight against him takes place under a dark sky filled with thunderclouds, while Jaki's fight with Zeus takes place under a clear sky with the sun shining brightly. In other words, the rivalry between Jaki and Zeus is a battle between God and the Devil, as well as a battle between light and dark.
Hien's appearance in Sora Yori Takaku, where it's shown that after graduating from Otokojuku, he went on to become a surgeon, which might seem incidental like all of the other big important jobs the other students are shown to have, such as Momotaro becoming the Prime Minister... until you remember that his cranebeak needles are a weaponized variation of accupuncture, which is a form of medicine, making it fitting that he would go on to become a doctor.
