I Love this Manga so much , and Im Happy this Manga is licensed in Germany *-* and the Sequel too (≧∀≦)
ahh im comming back when the Chapters is complett :/
my heart is so sad for this Q_Q
i hope Ayumi and Kotaru stay forver :3
Quotation from Chapter 66 ( there it is explained briefly)
http://www.mangago.me/read-manga/a_man_like_you/uu/m_chapter-66/pg-1/
Der Envy Stone can only Take Effect when its OWNER Jealous !
Envy Stone ( Lu Xuan)
The Fate Stone ( in Chapter 45 also everything is explained super )
http://www.mangago.me/read-manga/a_man_like_you/uu/a_man_like_you-chapter-45/1/
The stone shows you the person you love or want to see if I understood that correctly.
Fate Stone ( Siwon/Jinha)
A quote from Chapter 45
It says that the curse will be broken if the OWNER of the Fate Stone becomes one Body
an Soul , with his Loved one in his Dreams .
Since Siwon and Jinha did not become one, Lu Xuan is that evil ^^
Jinha makes everything so the Envy Stone shows no effect ( I feel really sorry for him how far he goes that he would even sleep with Lu Xuan to protect Siwon etc and I think he blames himself for that )
I hope I could help a bit with my bad English xD )
I have added the two links where all is explained too
Sorry if I forgot something or something.(づ￣ ³￣)づ