Well, he might serve magical drinks like Butterbeer-flavored coffee. His cafe could be a place where wizards and muggles alike gather. He could use magic to decorate the place with floating candles and moving portraits. Maybe his friends from Hogwarts would help out, like Hermione managing the accounts with her intelligence and Ron being in charge of the food tasting.
Well, perhaps it could involve Harry using his unique wizarding skills to create a magical - themed cafe in Konoha. The yaoi aspect might come in with the relationships between the male characters who frequent the cafe. For example, two ninja might start to develop feelings for each other over a shared love of Harry's special magical coffee.
It could be that they use magic to keep the pastries fresh all day. There might be a charm placed on the display case that constantly renews the freshness of the cakes and muffins. Something like 'Freshio' charm which ensures that every bite tastes as if it was just baked.
Hermione would be a great partner. Her intelligence and knowledge of magic would be invaluable. For example, if Harry opened a potion - making business, Hermione could handle the research and development of new potions, while Harry dealt with the business side like marketing and customer relations.
Well, he might use magic to create the most amazing pastries. His Firebolt skills could translate to lightning - fast kneading of dough. And his Hogwarts friends would surely visit often, like Hermione might help with the bookkeeping using her intelligence and Ron would be there to taste - test everything.
Well, it could be a magic item store. He might sell things like rare wands, enchanted potions, and magical maps. After all, he has a lot of experience with these things from his adventures at Hogwarts.
Well, perhaps the plot could involve Harry using his fame and fortune to open an orphanage. He might use his magic to create a safe and magical environment for the orphans. Maybe he'd teach them magic himself, or bring in some of his Hogwarts friends as teachers. It could also show how he deals with the challenges of running an orphanage, like getting enough funds and handling difficult children.
One possible plot could be that Harry uses his magical knowledge to create a bar with unique magical drinks. For example, he might serve Butterbeer with an extra kick of magic, or a potion - like cocktail that gives temporary magical abilities. He could also use the bar as a place for magical creatures and wizards to mingle, creating a new social hub in the wizarding world.