Rosario + Vampire x HP

Tenmei Mikogami (Chairman/Headmaster) takes in a young Harry Potter (fines him when he was left on the Dursley's doorstep?)

He could sense the power/potential Harry had even as a baby. (He also sensed the soul shard in his forehead).

Mikogami is a Kishin

Harry is blood adopted and becomes a wizard(Mage)/Kishin hybrid

Harry x Ruby Tōjō (?)

I want Harry to be a few years older than the main cast (who are for the most part 15 when the series starts and 18 when it ends).

So if I want Harry to be 18-21, he would 3-6 years older than the main cast.

If he is 18 at the beginning of canon, he would be a 3rd year, if he is 21 then he could be a teacher assistant or something?

Just realized Ruby is actually 16ish when she is first introduced, so if I made Harry 21 at the beginning he would be 5 years older than her.

Ruby is the same age as Gin.

Harry could be the same age as San Otonashi, like they could both have been in the newspaper club together (San as president and Harry as vice-president). And when Harry graduated he went on to assist his Father (the headmaster), so he stayed around the school. Maybe he could be a substitute teacher? Like seriously in this series they kept getting rid of teachers cause they were 'evil', the classes would need replacements! So till then Harry could substitute, and that could be how the main cast meet him? He could also help out Nekonome with the club in his free time.

Or if I really want him to be 21 when they first meet him he could be San's predecessor for the newspaper club.

So ages ( beginning of series)

Tenmei Mikogami (200+)

Harry Potter/Mikogami (21)

Tsukune Aono (15/16)

Moka Akashiya (15)

Kurumu Kurono (14/15)

Yukari Sendo (11)

Ruby Tōjō (16)

Mizore Shirayuki (15)

Kokoa Shuzen (12)

Fang Fang Huang (13)

San Otonashi (18)

Ginei Morioka (16)

Shizuka Nekonome (44-47)

Then add 3 years for their ages at the end of the series.

Kokoa, and Fang Fang were both introduced in Tsukune's second year of high school.

Gin was one year above Tsukune in school.

San was a 3rd year when Gin was a 1st year.

Ruby never attended the school, and I'm not 100% sure if she was/is actually the same age as Gin or if she was/is already 19 when she was/is introduced.

Nekonome-sensei could already be 47 when the series began or she could have been 44, not sure with the wiki stated ages!

So about Harry Potter canon events, since Harry was adopted as a baby by Tenmei, it threw everything off.

Firstly Tenmei destroys the horcrux at first opportunity.

And Harry is raised by his single dad in a world of monsters. (I imagine the headmaster would live there on campus, so Harry would be raised around the academy as a kid).

When he is old enough Harry goes to the Monster/Yokai elementary and middle school respectively.

Though when he is 11 he receives a letter (or 2) in the mail from magical schools (the first is Hogwarts addressed to a Mr. Harry Potter and the other is from Mahoutokoro addressing a Mr. Harry Mikogami).

The one from Hogwarts instigates an investigation about Harry's past/roots (though I feel like maybe Tenmei already figured it out, so maybe he just tells his son the truth of the matter).

But is more or less declined once Harry (and Tenmei) learn that Harry can stay with his regular education and just take night/weekend classes at Mahoutokoro and still get his magical education. The small family obviously go with the nicer choice (it helps that this school is actually in Japan).

But because Harry Potter declined his invitation to Hogwarts someone is sent to investigate (Minerva), and they are convinced that the decision made really is the best choice for young Harry. Though she does ask/insist that Harry (and his Father) should at least come and visit the bank, since she's sure his birth parents left things for him. (So the duo do visit gringotts at the very least and take care of the Potter family inheritance and have some other things looked into).

So Harry leads a rather normal life (for a wizard/Kishin hybrid), he studies and learns and trains.

Eventually when he graduates from middle school, he and his father take a trip back to England for the summer (he is 14-15) and well those things they had investigated last time finally come to a conclusion.

(They had the events of October 31st investigated, so the lack of trial for Sirius Black was looked into; information about Horcruxes was researched, and Voldemort's past was looked into in hopes of finding out valuable information about anymore Horcruxes. Which were found and subsequently destroyed that summer/trip. The prophecy was also looked into and declared a dud, since Harry wasn't around Voldemort was never revived (or at least his revival was slowed down even more), so Voldemort never got the chance to go crazy over that, so that was taken care of. Also anything of Harry's that was elsewhere was returned during that first trip (the cloak) when he was 11, which Tenmei (and the goblins) sensed power in, which led to an investigation of why, and later when the ring was found and identified led to explanations about the Deathly Hollows.)

Anyway a lot of stuff was accomplished that summer.

So Harry returns to Japan and starts at Yokai Academy, and joins the newspaper club.

His high school live isn't too insane, pretty average to be exact. He dates a few girls, becomes president of his club his third year (meets San and treats her as his little sister), gains his magical degree a year before he graduates high school and live goes on.

Once he graduates from Yokai Academy he 'apprentices' under his father in his free time, but he also goes onto higher education and gains a teaching certificate/degree, and a cooking license/degree(what would that actually be considered?) and a masters or three in magical fields (defense, sealing/runes, and healing), that all happens within 3 years.

Finally canon begins and Harry is 21.

The year a human is enrolled into Yokai Academy Harry becomes his father's Assistant and the cooking teacher (Since I didn't really watch the anime I'm gonna ignore the anime only cooking teacher Aspara).

[A lot of girls find him highly attractive, but they don't always do too well.]

He also helps out Nekonome-sensei with the newspaper club when she needs it since he was formally in the Newspaper club she runs (though he normally/mostly advises the Cooking club).

Tenmei Mikogami when he finds Harry goes to his friends Touhou Fuhai for help/assistance in removing the horcrux and making Harry his blood son.

Maybe in exchange Touhou has Harry become engaged to his great-great granddaughter Ling-Ling Huang who was born recently.

But she dies of an illness before they come of age to be wed and is turned into a Jiang Shi, and the arrangement is called off, though the two remain great friends.

So when Fang Fang realizes that Harry is there and the others realizes they know each other, Fang Fang simply says he was engaged to his sister before she died (much to their shock).