"The Assassin Who Became A Demon's Grandson"

Iruma's journey in the past in the human realm and attended an assassin school and how he will use it for advantage in the present here in the netherworld.

Crossover: Mairimashita Iruma kun! & Assassination Classroom

Credits to the rightful and original owner of the story(I already have permission to write here):
irumatheassasin in tumblr

https://irumatheassassin.tumblr.com/post/652431061752643584/chapter-11-the-assassin-who-got-proposed-on-live