I read this story about 2 years ago.
A class gets transported to another world. There, the main character gets abandoned for some reason. He can seduce any female character. He gets a butterfly friend. There is also another character which can seduce any man.
I believe you are looking for Because I Was Excluded Out of the Class Transfer, I Decided to Steal My Classmate’s Lover. I feel I probably don't need to mention this based on the title alone, but it is NSFW.
The main character has the skill [Underling Training (Lunatic Sexual)]. This skill allows him to "train" women. He is then forced out of the group by another character, who said his skill made the girls in the class nervous.
A couple chapters in, the main character has a butterfly who is his underling because of the skill. I did not see the character who could seduce any man, but I only skimmed the first few chapters. The site i found it on has the translations for the first few chapters from 2016, so at least the two years ago you said you read it.
