This title is a duplicate.

https://anilist.co/manga/105266/Koroshiya-S-no-Yuragi/ seems to be a duplicate of https://anilist.co/manga/105273/Koroshiya-S-no-Yuragi/ also it seems that the author on this one is incorrect. https://www.mangaupdates.com/series.html?id=155827
i suggest deletion of the 1st