Crossover: Ace Grown from a Seed

Hey, kiddo~ I've got a seed here that can grow anything you want~ Anything at all~ Luffy planted the seed. The first day, the second day, the third day... On the thirtieth day, it sprouted, grew leaves, blossomed, and bore fruit! But this fruit is a little strange! Fruit, month one: Babble babble Fruit, month two: Lu... Luffy... Fruit, month six: Hey! Who the heck are you? Fruit, month seven: That old geezer Garp can't have a grandson as big as you! Fruit, month ten: Hey! Luffy, what weird thing did you eat this time? How'd you get so big!? Fruit, month twenty: What are you crying for, idiot? I'm back, Luffy. ^^^ Luffy: Waaah, Ace!!! This time, promise me, we... we'll never be apart again!! Ace: Baka! This time... I won't break my word. We'll always, always, always be together, so stop crying, Luffy. Reader's Guide 1. This story is full of the author's pent-up feelings, inspired by a story written by a close friend! 2. The whole story is warm and cozy, roughly like Sherlock, with everyday displays of affection~ 3. This is a crossover featuring Hunter x Hunter, Harry Potter, and more. 4. Contains BL and BG! If that's not your thing, please leave of your own accord! Also, no personal attacks! Thanks! 5. No ranking checks or reposting of any kind. My friend's story: The Tale of How I Accidentally Got Kidnapped and Became Mrs. Malfoy My completed draft: One Body, Two People. The male lead is Marco. [Mutual pampering] My friend's completed draft: Boys, Just Do It! Don't Be a Wimp! Bird Sauce's QQ group and author page: Bird Sauce will occasionally post some weird stuff, so shh~ Nobody say a word~ Also, thanks to Hua Xiaomi and Mingchao for making the cover for me. It's super cute~ \(≧▽≦)/~ Theme: