For those interested in this story I highly recommend watching a documentary on the Kowloon walled city such as this one: https://www .youtube .com/watch?v=4YuNvIfM-YA
It really puts into perspective just how densely packed the city truly was, the living conditions, the city's history and eventually the end of it. Really feel for the characters' struggles, especially Weijing.
Does anyone know how to get the side story (in english or japanese is fine)
Yes, this one! https://www.cmoa.jp/title/252945/vol/2/
Read the Temple Scan trans if you want to understand what’s going on
Where can I read?
On their website Temple.scans. net just remove the first dot