Creator post new chapter when a target of RT has been reached (at least this is mentioned in chapter 1 and chapter 2, also mentioned in pixiv)
On chapter 2, the target was 200RT (It reaches 235RT when I post this, and chapter 3 already uploaded)
Although not mentioned, if chapter 3 has the same condition, it still need at least 77RT (currently 123RT)
If you'd like to see more chapter (at least from author, not my uploads here), probably you can help by RT the chapter 3's tweet, hoping
creator will post the new one when it reaches the target.
direct link to chapter 3 on creator's twitter