Cyrus Epimetheus a martial artist of the demonic cult offended too many people from both sides of the murim while trying to reach the peak of martial arts leading to him being betrayed and besieged on all sides. After his death Cyrus wakes up and meets the god of creation who sends him to the world of danmachi in the body of his seven year-old self with the purpose of helping the main character mature faster.

With a system in hand and his past life knowledge Cyrus intends to live a life free of worry while becoming the strongest by any means necessary.

(disclaimer) 
This novel will have a bunch of light novel spoilers. some of the spoilers heard will be canon and others will be rumors. 
this novel will not have any ntr. meaning Cyrus wont steal Lili, Hestia, or Ais (haruhime is debatable.)
In terms of romance I plan on having one or two with the possibility of three people with the main character.
the god of creation and the system will not place any restrictions on Cyrus except for helping bell grow.
finally I myself have not read all of the light novel and i'm fine with spoilers so please tell me if I make a mistake that completely messes with the story. tho keep in mind that as a fan fiction this novel will not be canon and can have a lot of differences.

epimetheus god

Danmachi: reincarnated as the strongest support character