If you views dislike my grammar, then you are free to take this chapter and rewrite as much as you want.
About six years later, Issei Hyoudou lived quite a life. He was just a normal pervert young man in high school which lot of events led to him becoming a dragon/devil and unknowable made his dream come true by forming a harem. During these six years, Issei manager to enter college and with Rias influence, him and his harem all went to the same college to be together. Rias was a beautiful young woman who went to the same school as Issei who is a pure blooded devil and became his girlfriend.
Issei and Rias both loved each other for a long time, despite Issei wanting a harem or Rias high rank in society. Issei and his harem plan a party at Issei old house, but before they travel there by car (to feel like normal people), Issei use a portal (which he got help from Le Fay) to travel to the Underworld to pay a special visit to Rias parents.
Risa parents love Issei as their own son and unknowable to him, that they made Issei Rias new fiancé. Issei thought to himself "I wonder if they will accept my offer to Rias" Issei sallow his own spit, nervous of meeting Rias parents without Rias by his side. Issei had grown quite a bit, Issei looked older and a little more mature, and no longer wear his school uniform but still had a lustful face. Issei wanted to meet Rias parents by himself to deciduas a very important matter about him and Rias.
Issei made it to the castle of the Gremory by the help of their maid without making a scene since they is a lot of people outside of the castle, possibly wanting to meet or speak with Lord Gremory who is Rias father. Issei went to the main hall where he saw Lord Gremory and his beautiful young wife, Venelana who look just like Rias which led to Issei thinking lustful thought about her.
Lord Gremory was surprised to see Issei but then grow a warm smile "why hello there son, it been a while hasn't it" Lord Gremory greet Issei which made Issei nervous since he feels uncomfortable by Rias father calling him son "hello Mr…. I mean father, it had been a while, sorry for coming here without making a appointment" Issei respond polity and bow a little since he is the father of the woman he loves "is no problem, you are basically part of the family" Venelan warm smile Issei which made Issei heart beat a little due to her beauty, but there is no time for that.
"So how is our daughter, Rias, she hasn't been acting selfish, hasn't she" Venelan mention Rias strictly which made Issei stop bowing and start acting serious "about Rias, there is something I wanted to talk about her" Rias parents were lost at the moment until Issei sit close to them "is it okay for me to sit here" Issei ask polity which Lord Gremory told him it was fine "you know that I loved your daughter very much, and that I'm willing to protect her" Lord Gremory nodded "yeah, that is why we choose you as Rias new partner."
Issei started to sweat when he was about to say something that he was fearing to say to Rias parents "I…I wanted to propose to Rias and make her my wife, can I have your blessing" Issei sounded loudly but a little shaky. Rias parents were surprised and confused at Issei word which made Issei thought to himself "oh no, they don't want me to marry their daughter, of course, why would a pure blood devils want a son in law who is a human turn devil/dragon."
Venelan was the first one to spoke "well it's great you want to marry our daughter but she already have a fiancé" Issei becoming heartbroken after hearing what Venelan had said "what…what…who it is" Issei was sadden but in rage, thinking another Riser is after his Rias, well it doesn't matter to him, he will beat the crap out of the new guy to get Rias back. "who is this new guy you made Rias marry to" Issei trying to act calm but couldn't hold it for long.
Both Venelan and Lord Gremory looked at each other confused "son, it is you, you areRias fiancé" Issei heard what Lord Gremory said which shocks him even greater than he though "what" Issei spoke softly "well of course, that's why you and Rias took the ritual at our sacred temple and when you two pass, you became Rias new partner, meaning her new fiancé" Venelan told Issei.
Issei then thought back to that time and realize how the test seem strange and Rias blushing most of the time, that was a test to decided if I was good enough to be Rias husband. Issei then went to a wall and put his head on the wall feeling like an idiot for not noticing this sooner. Issei then hear laughing coming from Rias parents "well, I guess I'm glad to pick you as our son in law, Issei" Venelan was laughing which was strange to see which she is usually calm, even Lord Germoy "I guess you are a good match for Rias, she could need more joy in her life" Issei didn't know how he should feel at the moment but smile to see them happy.
Once thing calms down, they went back to chatting "since you wanted to marry our daughter now, I guess we should inform Rias about you plan" Venelan ask Issei "I'm sorry but I don't want you to tell Issei about this" Rias parent were confused at Issei "I'm very happy that you choose me as Rias husband" Issei give a warm smile "but I want to propose Rias by doing it the right way, the way where she can remember this as long as she want" Issei said sounding confidence.
Rias parents were surprise at Issei idea but smile "well if you wanted this way, then that is alright with us and we will give you our blessing, right dear" Venelan smile "that's right, but under one condition" Lord Germoy sounded serious which made Issei nervous "you have to call us mom and dad from now on" Lord Germoy then smile again which cools him down "and if you don't call us mom and dad, then we will reject you as our son" Lord Germoy went back to being serious "yes Lord…. I mean father" Issei respond, Lord Germoy "that's better" Issei then realize something else.
"There is also something else I wanted to say" Issei sounded nervous again "I have a dream to make my our harem, and of course I want Rias to be in it, but I was wondering if you are okay with this" Issei now thinking that they would reject Issei dream but then was surprised at Rias parent next word "sure, go ahead" Issei face landed down "what do you mean" Issei fearing for the answer.
"Well while watching both you and Rias group, I notice that despite you dating and loving our daughter, the girls are still in love with you, and wouldn't give up on you anytime soon. I think you should build a harem so all the girls will be happy since they will have you" Venelan said smiling "but we will only allow it for one thing you have to do" Venelan then went back to being serious "what is it" Issei is nervous again "you have to make Rias the lead female of your harem" Issei then cool now "of course, I love I Rias very much, I would be very happy to make her the lead" Rias parents smile and both had a nice long chat.
After hours of chatting with Rias parents, about child names, holidays, and thing like that. Issei went back to the human world where he makes plan to propose to Rias and make her very happy.