Gowther is a doll. Being not human, created but an intelligent demon and possesses the special ability to invade minds, Gowther is highly intelligent and curious of emotion. He reads a lot of books which contributes to his high intellect but only because he’s curious of emotions and reads as an attempt to understand humans and their feelings.
Gowther befriended a princess who eventually became sick and she died not long after they’ve made love. Gowther was seen by the dead princess’ side and got accused of both rape and murder. He was branded the Goat Sin of Lust. Imagine, right after receiving love. Tut tut tut tut tut.
Gowther’s lust was for a heart, the thing that stores and understands emotion. He sees growth amongst his friends in regards to mind, physique, emotion and he sees how this enhances relationships and he associates that with the heart.
Gowther released his lustfulness towards wanting a heart after realising that he always had one. Half the work is done in the deeds, by carrying out actions of love and care towards his friends he too has shown growth just like all the other members of the group. He understood that harmony can be found amongst many when we look to see what we can give instead of seeking what we can get.