She just needs a bit more persuasion!

"...what?" Rias asked when she saw everyone staring at her. "I'm just following Master's example of putting all our cards on the table."

Issei sighed as Asia hesitated. "...I don't know... I do like Issei, but... Lust is supposed to be a sin, and while I don't know why anymore, surely God has a reason..."

"...I don't think any of the so called Seven Deadly Sins in of themselves are a problem," Issei said after a moment of consideration.

Asia blinked and stared at Issei. "...what do you mean?" she asked him.

"I mean... Well, think about it, all of them are just... Natural human traits, aren't they? Hell, even necessary for survival," Issei explained carefully.

"I... don't follow?" Asia asked as Rias and the Peerage watched intently to see where Issei was going with it.

"Well, Gluttony is necessary, because everyone needs to eat to live, and of course, eating is enjoyable, an incentive built in to ensure we do it," Issei explained. "Wrath is a natural response to being wronged, if you don't enforce some kind of consequence to wronging you, you become a doormat, and someone easily taken advantage of. If someone hurts you or those you care about, you're well within your rights to retaliate, even if only to drive off the aggressor, and anger is a powerful driving **** that can be used. Then you have Pride, which is when you feel a sense of accomplishment due to your achievements. It can help one strive to better themselves. Sloth is also key, everyone needs to rest their bodies and minds from time to time. Whether it be from work, day to day drudgery, painful and traumatizing training..."

"Yeah, no, you're not getting out of evasion training that easily," Rias told Issei flatly, and he sighed as the others chuckled.

"Worth a try. Then we have Envy, which, like Pride, can also be a powerful motivator to better ourselves, so we can have things or traits we want, and working to get such things for ourselves isn't a bad thing. Greed is much the same way, and we do need things and money to get by in the world, so trying to get enough to live comfortably is not bad. Then we finally have Lust. Which is basically literally how we reproduce and continue the species. All of these things are an essential part of having what we call humanity, whether we be actually human, Devil, or Angel. So what is it that makes these things sins?"

"...I'm not sure?" Asia asked.

"I think... The answer is excess. When you have these traits to the point where they become self destructive, or even outwardly destructive. Gluttony in excess can lead to consuming too much, and becoming unhealthy. Wrath can lead to you destroying everything around you in a rage. Pride can become arrogance, and lead you to overestimating your abilities, getting in over your head, or becoming **** to ask for help. Sloth can become laziness. Envy can lead to you trying to tear others down to your level rather than rising up. Greed can result in one taking more than they need, and giving little or nothing back. And Lust... Well, I don't want to go into how that in excess can go wrong..."

Issei rubbed the back of his head as he continued his thoughts. "Point is... If you want to join the harem, there's literally no reason not to, so long as no one is forcing anything that isn't wanted on anyone else in it," he finished.