what book II is all about (summary)

The book's name:

Book II: War

this summery will determine whether you'd be interested in following the whole 10-13 chapters:

after Zei's defeat, Avatar Yin realised the power waterbending has and wanted to go to the northern water tribe to master it. little did he know that the leader of the tribe Katsumi had other plans for him. she forced Yin to close the northern spirit portal and lead a war against the southern tribe and Republic city because they refused to close their portals. what will happen and how will Yin get out of this mess?

A really fun coincidence, my favorite early chapter of book I was chapter 5 and mime in book II is chapter 5 as well