I think MC kills these six demon lords in his period that's why they don't appear in nano machine but only those three ancient yokai appears. (

Myst, Might, Mayhem - Chapter 73

@Sam What do you mean by nano machine? Is it connected?

Kamran Khan

@Kamran Khan yeah

@Kamran Khan this MC is the founder of heavenly demonic cult from nano machine

@Sam Really!!! Where did you read that???

@Kamran Khan this is the prequel to nanomachine