Like two sides of a coin, every person has two sides of their personality. Everyone sees Cedric Diggory as some perfect golden boy, a good natured guy with a kind personality that has everyone around him fooled. People literally swoon over him but with you, he's like a completely different person. He's like your shadow, always following you around never really leaving you alone and he keeps popping up everywhere. It all started when you first met him when you were in the second year and he was in the fifth year
You were in the same house as him but you never really talked to him that much even though he was the prefect of your house and the most popular guy in your house. You never really concerned yourself with the popular people at Hogwarts, you tried to stay out of drama. But unfortunately drama came knocking at your door. You were getting picked on by some Slytherin 4th years and they started getting all handsy with you making you feel uncomfortable. You mentally cursed yourself for leaving your wand back in your dorm and when one of them tried to touch your shoulder again you yelled "BACK OFF!" and raised your fists threateningly. They chuckled and one of them leered "Oh look what we have here fellas, little Ms. Hufflepuff is trying to tough, how cute'' but before you were about to lose your temper and punch them in the face by using your mad and awesome karate skills, a blinding blue flash of light came from someone behind you as they were all pushed back
Their eyes widened with surprise as they scurried away and when you looked back, you saw Cedric Diggory with a pissed off look on his face. That was most certainly a first you thought. You never saw him getting angry over anything but now he clearly was pissed. "Sorry you had to see that, I hope you're all right'' and you replied "Thanks for your help Cedric, but I could have punched them in the face you know?" and he chuckled and replied "But you'd get hurt and get in detention for doing that. Professor Snape's been in an extremely crappy mood these days ever since Neville Longbottom's Boggart incident'' and you smiled to yourself and replied "Yeah, I've heard of that. Well, I should be going to Transfiguration before Professor McGonagall gives me detention for coming to class late'' and he told you to go, he'd catch up with you later after your classes were done
Sure enough, he was true to his word and caught up with you after your classes were done for dinner. He sat next to you, asking you how your day went. You found him to be quite charming and nice, he was friendly and caring to you like a big brother you never really had. Cedric seemed to take an awful lot of interest in your life, enquiring about your day, classes and what you liked you do during your free time and stuff like that. He was genuinely concerned for you and ever since he saved you from those bullies, his mind was occupied with you. He wondered how such a naive little angel like you was all alone, he promised himself to keep a watch over you to make sure you were safe and okay
If there were any people bullying you or something Cedric would pretend he's talking with them but in reality he's probably intimidating the hell out of them. He cared for you like a little sibling. He didn't like it whenever you were sad and he would always make sure to cheer you up by bringing you your favorite Honeydukes sweets and whatnot. However if you like drinking Butterbeer then you'll have to say goodbye to it since he won't allow you to drink it. He knows there's alcohol in it and he doesn't want you drinking it. He'll hang out with you whenever you guys go to Hogsmeade. You can also bet your pocket money he'll have some other Hufflepuff students report to him about your day to day activities. Little snitches
The thing about him is that even if you have loving parents or not, he'll still want you to be his little sibling and he'll tell his parents about you. Unfortunately for you they've decided it's a good idea for them to adopt you. Cedric thinks he and his family can take of you better than your own family can and he's become so delusional he absolutely refuses to see reason and be logical. If you scream and cry and beg, it won't be of any use since they'll just coo and tell you how adorable you are. Also you won't be going back to Hogwarts once you're in the Diggory household since they think it's too unsafe for you. So yeah good luck dealing with them