More infos on Pine-Bamboo-Plum :
https://en.wikipedia.org/wiki/Three_Friends_of_Winter
https://en.wiktionary.org/wiki/%E6%9D%BE%E7%AB%B9%E6%A2%85
This is a three-rank system based on grades or classes of certain items : “pine” = the top rank , “bamboo” = the middle rank ,“plum” = the lowest rank .
Page 16 : There is a Japanese idiom : "Along comes a duck with a leek on its mouth" , meaning a very convenient thing , like a duck has come to our dinner with its own seasoning . The Pokemon Farfetch'd / Kamonegi also came from this idiom .
Page 22 : she probably refers to Dragon Ball 's Ultra Divine Water ( Chōshinsui, lit. "Super God/Divine Water") is a magic water that will draw out all of the drinker's potential if they can survive its poisonous and painful effects.