After the First Great War and death of Four Great Satans, an immensely powerful child, Sirzechs was born in the House of Gremory. He was the son of Zeoticus( of Gremory Family) and Venelana(of Bael Family ) and inherited the trait of [Destruction] from his mother’s side which was a prominent trait of the Bael Family, a top-tier clan among the 72 pillars.

17 years later…

Sirzechs, who was fond of teaching music to little children and enjoyed interacting with people of his Estate, was invited to a “social gathering” at the capital city of ‘Luciferd’.

Soon after arriving, he witnessed a commotion between an upper class man of Oriacs and a descendant of Satan Beelzebub, who was harassing the upper class man because the “quality” of crops he sent this year were inferior to last year’s. It was precisely because a disease had plagued their domain.

The scenario was quite common for most folks and planted a seed of fear of “immense” power possessed by descendants of Satan in the eyes of people.

There were, however, a few exceptions. The ones who looked at the scene unaffected were Sirzechs, Serafall Sitri, Ajuka Astaroth and Falbium Glasya-Labolas, who were childhood friends and extremely powerful individuals.

The situation became worse and eventually Sirzechs stepped in to save Oriacs’ heir.

He diligently fought with Beezlebub’s descendant, cancelling his attacks but soon the situation ran out of hand and someone had to step in to stop them.

That someone was the Grafiya Lucifuge,who was the direct lineage of Lucifuge, the descendants of Satan Lucifer.

Sirzechs fell in love with her, the very second he saw her, it was love at first sight.

They had a formal introduction and after the revelation of Sirzechs’ immense power, she was appointed to look over him.

60 years after the birth of Sirzechs…

The Satanic Families( except Lucifer ) were ruling over the underworld, planning to start a Second Great War after the ascending the throne. The Devil Kingdom, which was on the verge of an inevitable Civil War, was divided into Satanic and Anti-Satanic (The Resistance) parties.

We see Sirzechs bidding farewell to his choir after a final rehearsal. They were going to the capital for singing a song of peace as official Gremory choir.

Serafall, Euclid and Grayfia arrive at the Gremory Mansion, Grayfia tells Sirzechs to go and help Ajuka who had been to city of Agreas for some stuff.

Euclid warns Sirzechs not to talk to her sister while Grayfia and Serafall were out for a chore.

In Bael Domain a secret meeting was being held among the pro-Great King noble families, during the meeting the news of revolt at the capital was received.

Sirzechs, after recieving the news, left Agreas and reached Luciferd to search and save his dear children who had come to perform the song of peace.

But he wasn’t able to save them…..

This made him drown in despair.

Meanwhile the descendants of Lucifer reach to a conclusion of using their secret weapon( the Malebranke ) known only to them when things get worse.

After six months of the Civil War…

The Satanic Fraction continued to rule and the Resistance was under the command of Great King Bael and Grand Duke Agares.

The War initially favoured the Satans but after the joining of Sirzechs, Serafall, Falbium and Ajuka, the tables had started to turn.

One of the deciding battles was being fought between Ajuka Astaroth and Tsfarme Teleac Leviathan.

Ajuka and Sirzechs were wielders of great power, far greater than anybody had previously witnessed.

Tsfarme was very strong and tried everything she could but Ajuka easily and completely won, killing her in the process.

When Rizevim, the son of [Morning Star] Lucifer, got the news of Tsfarme’s death, he found it boring and refused to do anything.

Another battle was being fought between Serafall and Asmodeus.

Initially the battle favoured Serafall but after Grayfia’s arrival, the battle lasted for ten days until Sirzechs,who had previously been fighting Beezlebub’s army, arrived.

Meanwhile the descendants of Lucifer awaken two of the Malebranke including Barbaricha,the Deputy Commander of Malebranke.

While Serafall fought with Grayfia, Sirzechs went to fight Asmodeus where he met Euclid and the very descendant of Beezlebub he fought when he was a child, who transformed himself into a fly-form Chimera which was the power of one of the Malebranke, Skullmillione’s Power!.

Malebranke often referred to as [Satanic Arms] resembled sacred gears made by God of the bible. They were living weapons created by the Four Great Satans using special crystals at Agreas.

A talk between Rizevim, who was leaving Lucifard and Beezlebub’s head, Veried takes place where Rizevim tells about his “Sacred Gear Canceller” and that he has no interest in the Civil War.

The Chimera emitted deadly poison which was inhaled by Euclid, making him unconscious. Sirzechs saved him and eventually decided to fight it all alone after all the troops had backed down.

At the border of Old Erigos domain about 200 of Satanic army troops were firing magic at resistance troops guarding the perimeter.

But they weren’t able to damage Falbium who had stepped into the battlefield, as he was born with “Absolute Defense”. Even the strongest of the strongest weren’t able to deplete Falbium’s defences.

He also had power to reshoot the attacks charged at him and did the very same thing which made the heads of houses of Agarialept and Fluretti fall on their knees.

Meanwhile, Sirzechs defeated Chimera while demonstrating his True Destruction Form.

That was the first time Grayfia had seen that form.

…..

Several years had passed after that unclassified incident, the head of Lucifuge called for Sirzechs and told him that Lucifuge is better destroyed than letting Euclid take the throne as he was mistaught. He also told him to take care of Grayfia as she liked him and loved visiting Gremory household.

Sirzechs, Serafall and Ajuka defeated everyone who dared to challenge them and finally after the death of Veried, the head of Beezlebub, the Civil War ended.

Months later the four of them were asked to inherit the Satan’s throne by Zerakum Bael.

While Grayfia was helping Sirzechs to reconstruct the Gremory household , Sirzechs said hat if he were to inherit the Satan’s throne, he would take Lucifer’s throne and Grayfia told him that she would stay by his side forever.

And then…..

Sirzechs proposed Grayfia and she scolded him for choosing such a bad place but eventually said ‘yes’ because only she could tolerate a Prince with such a bad humour.

The Malebranke was sealed again.

A few hundred years later, something festive happened in the Gremory Domain, Sirzechs and Grayfia’s marriage.

And after two more years….

“Sirzechs, my little Sona is so cute”,Serafall told Sirzechs about her new born sister with a cheerful look in her eyes.

At the same time, Rias was born too…

Sirzechs told Grayfia that he would like to bring out the reformation .. where not only Devils but everyone would be able to live in peace.

Grayfia asked him if he meant the reformation of underworld and if so what kind of opportunity would it be.

To this Sirzechs replied that it would be the rising of a new hero, someone whose sole existence would lead the people of Underworld , instead of trying to settle matters using power like they had…someone who would not be imprisoned by the status quo….

Grayfia interrupted him and said that would be nice and in response to that Sirzechs told that he would then write a song for that hero, a song of peace.

Years later…..Sirzechs wrote The Oppai Dragon Song.