Start by Eating Jake Jake no Mi

Serafall had become Masa's. 

While this made everyone conflicted, especially when the most powerful female devil in the world had become his woman, it did more good than harm to their family, so why should they think too much?

More importantly, when they thought of Serafall's power that could turn kilometers of wasteland into a frozen wasteland and completely change the climate, temperature, and terrain into freezing land, and Masa's ability that could go completely unscathed despite being hit by such an ability, all of them knew that they should just keep quiet about everything, and support them.

As for the rules that might stop them from being together, who cares about those rules? 

Anyway, it was impossible to stop the two, and they just enjoyed themselves. 

Regardless, as Masa's fiancee, while Ravel was speechless, she accepted it quickly since she knew well that this couldn't be stopped, especially with Serafall's rampage and how their feelings had grown. Frankly, it was amazing that he chose her, so she didn't ask much, but then again, as she was his fiancee, it should be okay to have a little selfishness, right? 

So, when they returned, Ravel clung to his waist as she lay on his lap. 

"Masa-sama, your tea." 

"Thanks, Asia." 

As Masa accepted the tea and sipped it gently, he continued to rub Ravel's head like a petting dog, which caused Ravel to narrow her eyes and breathe heavily, especially with how nonchalant he was, as if he treated her like a real pet. 

Watching Ravel being treated, Asia showed a slightly envious expression, but she held it in, especially after she had been held by Masa when Ravel wasn't around.

Still, a question emerged in Asia's mind. 'Did she take his virginity?' 

If so, then she had to apologize to Ravel since even if Ravel was Masa's official fiance, his virginity was taken by Asia, but Asia didn't regret it and felt quite happy somehow. 

Regardless, if Raynare, Mittlet, and Kalawarna knew what Asia was thinking, they would snort, thinking that Asia was as naive as ever. 

Nevertheless, Masa had to say that Ddraig's ability was quite good, especially when he could multiply the flavor and nutritional value of the tea with this boosting ability. Yes, as he had devoured the Boosted Gear, it meant he had gotten everything about Ddraig and everything within this Longinus.

'Probably, the fate which it will become?' 

However, just the boosting ability that Masa could use, similar to the ability of the Moa Moa no Mi, was good enough. At the same time, he also had confirmed that he could develop this ability in a way similar to the Moa Moa no Mi, so he knew that he didn't need the Moa Moa no Mi, which he had given Van Augur. 

Mystery. 

The supernatural, including gods, demons, and all other creatures in the myths, existed in this world, which meant instead of being limited by the law of physics, everything moved based on a mystery, which was something "abstract" and couldn't be explained. 

If someone, something, or anything wished or dreamed, then anything was possible. 

It was like Issei, who wished for an ability to talk with boobs, which was then such an ability was created. 

Ddraig, who was a Heavenly Dragon, had that mystery, which allowed him to develop anything that he wished to be, but unfortunately, as a dragon, everything that he needed could be gained easily by just robbing or going on a rampage. 

Regardless, Ddraig had become Masa's property, and he had to admit that it felt great to devour such a being, which made him wish to get more somehow. 

Nevertheless, as Serafall had become him, Masa thought about his plan with everyone that he trusted.

"Books?" 3x

When Serafall woke up, she quickly asked Masa to rub her too, which she also laid on his lap like Ravel, then let her head be rubbed like a pet too. 

Instead of being worshipped and treated in a special way, it seemed they loved being treated in a humiliating way to degrade their values. 

Well, everyone had their own interests, so Masa decided to respect that, and because of that, he could also trust them. 

"Do you want to collect all the books in this world, Masa?" 

"If possible." Masa nodded and said, "I plan to collect all the books, whether they are about magic, unique knowledge, stories, or anything else, into one collection for our family." 

Unlike the Masa of Mahouka, who developed and tried to peel the law of physics slowly so he could peek at the root of the world,

The Masa of One Piece tried to gain a seed of power for all of them so they could become even stronger. 

Or the fourth Masa, who tried to develop the strongest martial art. 

Masa of DxD thought that he might as well collect all the mysteries in this world and then compile them into one. 

The Sacred Gear and Longinus might be powerful, but gaining them meant that he would become a target, being seen as someone dangerous who wished to bring a war to the world. 

If Masa was the strongest being, it would be wonderful, but even if he had enough power to destroy the world, such as by creating millions of nuclear bombs and then enhancing all of them with boosting power, it didn't mean that his opponents were weak, especially those Dragon Gods, and the gods from Hindu myth. 

Those were dangerous, and while Masa could protect himself by escaping to outer space, which was the realm that those creatures couldn't control, it would be different with his family. 

Yet, even so, Masa wished to improve, so he wished to get all the knowledge, genes, and anything, including the long-lost technologies that existed before the time of their myths even existed. 

Everything in this world was ready for him to uncover, and instead of dabbling with the technology, Masa knew that he should go all out with the mystery, miracles, and everything abstract in this world. 

At the same time, if it was knowledge, everyone would let their guard down toward him as no one thought that he would use knowledge to control the world.

Still, whether it was Serafall, Ravel, or Asia, they were all fascinated and fell for him even more when they heard Masa's words as he planned all of this for their future, especially for their children with him. 

Kyun~!

"That's a great plan! I will help you!" 

"I will get all the books on the House of Phenex and those who are close to our family." 

"If you need anything, I will help you, Masa-sama." 

Compared to the Rating Game, which was just a place to have a fight, they felt that Masa's goal was grandeur. 

"By the way, have you thought of the name of this plan?" Serafall suddenly asked. 

"Plan?" 

"Of course! Every plan needs a cool name! So, what will you name it?" 

Watching their excited expressions while Masa was speechless, he thought for a moment and said, "Index." 

"Index?" 

"Index Librorum Prohibitorum." Masa ignored their reactions and said, "That will be the name of this project." 

Using the name of the list of the heretical and banned books by the Catholics, as expected, this guy was a devil! 

Well, they loved him, though. 

Still, when they wanted to be pampered by him, helping him collect books as a method to be pampered more, the door of his room was suddenly knocked. 

Knock! Knock! 

"Masa, can I enter?" 

"Aunty? What's wrong?" 

As the door opened, Misla's beautiful face appeared before him, but somehow, Masa noticed her expression was a little strange, and instead of him, she focused her attention on someone else, which made her follow her gaze and look at Serafall, who smiled viciously in his direction. 

"..." Masa. 

However, as someone of her status, Misla quickly returned to her calm and said, "Rias Gremory, come to visit you." 

"Hmm?" 

Masa tilted his head and asked, "Is Sirzech Lucifer also coming with her?" 

"No?" 

"Then, tell her I am busy." 

"...." Everyone. 

Yes, Masa didn't lie since he was busy, especially when someone begged to summon him.