Worldwide Apocalypse: Starting With Max-Level Skills - Chapter 21: Exclusive Mission!

In the city of Graheel, a small antique shop sits quietly mixed in with all the other shops. Its unassuming appearance is easily overlooked by many. However, this store and its owner has a terrible secret. A devil lives in that building. The owner of the store, John Li, an enigmatic figure whose origins and intentions are unknown. The desperate from around the world, often unknowingly, come to him in search of salvation.A red witch thinks the owner is an ancient creature, a white fox calls him a wizard of eld, a warrior believes him to be a spirit, and a holy woman declares him a god. This mysterious individual and his customers would stand at the center of a strange series of events. From the store owner John's perspective, he has no idea what's going on. He really was just an unlucky dude that got caught up in some crazy stuff.

He is a young man without a spirit root. It is believed that this denies him the chance at cultivation. However, a mysterious lady imparts a Supreme Demon Classic to him and from then on, he starts his path of cultivation.
He undergoes a total transformation to emerge as the most fearsome and powerful fiendish demon in his era, that even immortals and fiends are fearful of him, and saints are at his beck and call.
Mastering the Supreme Demon Classic is the turning point in his life. He is able to unleash his immense and divine power from within, illuminating the entire universe!

- Description from Novelupdates

There are 5 books on the 6 sworn brothers in a serial called streamer (流光系列). ‘They are rich, handsome and powerful. These book are on various types of love as well as on the bond and mateship between the brothers. Book on youngest 6th brother.

Chen Yu Bai (3rd brother) & An Xiao Yi – Chen Yu Bai is a sharp, domineering & cool man whereas An Xiao Yi is a foolish, childish & innocent girl. He is her boss & she is his secretary. He bullies her yet at the same time will not hestitate to protect & shelter her. Thus, she can always rely on him. Their relationship is a funny one on how opposite attracts.

Li Wei Ran (5th brother) & Qin Sang – Li Wei Ran and his cousin Qin Song fell in long with Sang Sang who is An Xiao Yi’s best friend. Sang Sang sees Li Wei Ran as a good man. He is polite, patient and passionate whereas she is independent, intelligent and interesting. They are a perfect pair but she is afraid to love so he has to work hard to convince her he is worthy of her love..

Short sequel on their children.

“Wife! Come here!”“No!”She always thought he was aloof, but after getting the marriage certificate, the aloof military king immediately transformed into a wife-doting maniac.The husband indulges his wife in countless ways, Lily Turner finds it extremely exhausting, her protests go unheard, her pleas are ineffective, she wants to escape, but whenever she tries to climb the wall, it rises higher, leaving her in tears!When asked about the reason for his limitless indulgence, the young master responds astonishingly, “The one who dared to trick me into marriage, it's only her!”The woman beside him rolls her eyes at him: she is the one who got deceived, okay?