"Crappy luck" is an inadequate translation for 腐れ縁, which means "inescapable relationship". Have a nice day.
https://kotobank.jp/word/腐れ縁-483215
https://kotobank.jp/word/腐縁-2031289
https://dic.pixiv.net/a/腐れ縁
Mostly good, but some small issues. The "裏" in 裏主人公 and 裏ヒロイン doesn't mean "secret". It just means "other side", not unlike how "B-side" would be understood in English when there's something of a split narrative. Examples of 裏主人公 are Reiner from SnK and Sasuke from Naruto.
"ヤな奴" in Miko's...