Apocalypse - Evil Shelter System - Chapter 17: I Can Please You, But I Have a Condition

One of the seven strongest people on the continent, the King of Mercenaries. He started a war to avenge his fallen family and destroyed territory but failed and lost his life. However… “Wow, I’m alive?” I returned to the past, back through time. A perfect opportunity to right my regrets and reverse everything. It doesn’t matter if people around me point fingers, calling me a scoundrel, or dismiss me as tr*sh. Because… “I’ve got a plan.” “What plan?” “A plan to destroy everything.” There won’t be a second failure. This time, I’ll wipe out all my enemies. …But first, I need to rebuild this damn estate.

Julietta, born as an illegitimate child of a nobility, is raised in an opera theatre to hide away from the eyes of the noble’s main wife.

Dear comrades, masters, priests, masters, fairies, demons, and leaders, welcome to my world and enjoy the supreme pleasure and supreme enjoyment brought by traveling through various worlds (funny laugh).

- Description from novelbuddy

The story is about a man whose compulsive tendencies make it impossible for him to keep a job, and a young girl who skips school and loves insects. The two meet, come to support each other in reintegrating into society, and fall in love. There’s a problem, however: namely, the parasites in their heads.