Okay, so this is what my brain came up with after watching the ending of The Fault in Our Stars and listening to Ed Sheeran's "All of the Stars". This takes place around Season 3 of the series so I'd put Hiccup around maybe 17 while Zenna is about 18 years old. From what I remember, season 3 of Dragons is called Race to the Edge.

Enjoy!

Note: I do NOT own HTTYD, HTTYD 2 or the DreamWorks Dragons: Riders and Defenders of Berk. All rights go to Cressida Cowell, Dean DeBlois and DreamWorks Animation.

Chapter One: Writing the Letters

Stoick the Vast was worried.

His only son, Hiccup Horrendous Haddock III, was just sitting on the steps of the Great Hall with a depressed look on his face. Normally the 17-year old Pride of Berk was always running or, more accurately, flying about the island in search of new adventures. Not a day passed by when he and Toothless would go flying off to Thor knows where at morning and coming back at sunset to talk about a new land or new dragon they've encountered on their little excursions.

Today was not one of those days.

Stoick saw that, no matter how many times Toothless tried to spur the one-legged Viking teen to get off his lazy butt, Hiccup would just sigh and stare straight ahead.

Finally the great Chief of Berk adjusted his fur cape and went to sit beside his son. Hiccup regarded his father for a few seconds before sighing again and going back to vacantly staring at nothing.

"So…what's troubling you?" Stoick asked carefully. "Nothing, Dad…" Hiccup mumbled, putting his chin in his hands. Stoick raised an eyebrow. "The way you're acting all depressed tells me otherwise," he told his son. Hiccup just sighed again, his shoulders slumping forward.

Stoick sighed and shook his head. Whenever Hiccup was depressed, it was easy to see. The hard part, however, was helping the boy snap out of it. And since he was still working on completely fixing the previously strained relationship he had with his son, Stoick was no expert in that certain field of parenting. If there was anyone in the village who could help with this dilemma, Stoick was already racking his brain for a list of candidates.

Astrid? No, she was out training with the other Riders.

Gobber? No, he was still too busy with orders at the Dragon Armory.

Zenna? No, she was at Greece…

…Oh…

Stoick's eyes widened in realization of the cause of Hiccup's sudden lack of interest in, well, life in general and looked at his son. Hiccup let out a deep, long sigh that was filled with longing and sadness. His emerald green eyes reflected those two things clearly as well.

"You miss Zenna, don't you?" Stoick asked him. "It's been two years and six months since Toothless and I last saw her and Stryka, Dad. Thirty whole months since they left…" Hiccup said sadly before nodding. "Of course I miss her," he added before going back to his depressed staring again.

Stoick's eyes softened and he gently patted his son's back. He missed the one-eyed Fiersome girl as well. Berk lost some of its cheer when Zenna left. But everyone knew they'd see the lass again soon and went on with their lives. Hiccup, was a whole different story.

Toothless was rather glum for the first few months without Stryka, his beloved mate, at his side but soon got over it and was back to his usual happy and hyper self. His Rider, however, was beyond glum for an entire year.

Hiccup would always go to the Fiersomes to greet Henna and Edgar before asking if Zenna was home. Then he'd remember that Zenna was no longer there and leave with a sad face. Oh sure, he hung out with his friends and went out with Astrid all the time. But it was Zenna's companionship he always craved. Stoick remembered that the day after Zenna and Stryka sailed away for Greece was the hardest day for Hiccup. The poor boy put up a façade and tried his best to be cheerful. Later that night, Stoick went upstairs to tell Hiccup goodnight only to find his son crying like he had never cried before and whimpering his surrogate sister's name over and over again.

When Zenna had left, she had taken a piece of Hiccup's heart with her.

"Why not write her a letter, then?" Stoick suddenly suggested. Hiccup shrugged. "I did. Two weeks ago," he replied. "Well write to her again," Stoick told him. "Dad, she's probably just gotten my last one. I don't want to sound too clingy…" Hiccup said, turning pink with sheepishness. Stoick thoughtfully ran a hand through his thick beard. "Maybe if you write her a letter, and I mean really write her one, it will make you feel better. You won't know until you try," he then told his 17-year old son.

Hiccup thought about it for a few minutes before his face lit up with joy and hope.

"Thanks, Dad!" Standing up, Hiccup ran to his house. Toothless, who had been lazing about on the steps, looked up at Stoick and growled curiously, his head tilted to the side.

"Well Toothless, it looks like you won't be able to go flying today," Stoick chuckled, earning a disappointed huff from the Night Fury.

Upstairs in his room, Hiccup dipped his quill pen into the large bottle of colossal squid ink given to him by Trader Johann and put a stack of papers on his desk. After taking a moment to organize his thoughts, Hiccup put his quill pen to the blank paper and began to write.

He wrote and wrote and wrote and wrote, stopping every now and then to massage his left hand before going back to writing. Hiccup wrote, checked, double checked, revised and edited his letter several times. Pretty soon, crumpled paper surrounded his desk and littered the floor.

Then, just as the sun began to set, Hiccup finished his letter and had placed it in a sealed envelope. Going outside, Hiccup went straight to the docks. To his luck, a ship bearing goods that was going to the island of Kos, where Zenna was studying, was about to leave. Slipping a few gold coins into the captain's hand, Hiccup whispered his wish to have his letter delivered to Zenna as soon as possible.

The captain was amused at the Chief's son's request and promised to deliver it personally to Zenna, whom Hiccup described to him in great detail.

'I hope she gets it soon…' Hiccup thought hopefully as he went home for dinner.

Meanwhile on Kos, Greece at the exact same moment…

Hippocrates was worried.

Zenna Arrowhead Fiersome was currently sitting outside in the gardens of the school, Stryka dozing in the grass, with a sad look on her young face. A stack of scrolls she had borrowed to study were left forgotten at her feet. The young Fiersome lady sighed wistfully and looked off into the distance.

Finally Hippocrates went to the gardens and sat at her side. Zenna nodded respectfully to her teacher before sighing again.

"Now then, what troubles you, young one?" Hippocrates asked with concern. "Nothing, Teacher…I was…just thinking of my best friend…" Zenna replied, shrugging. "Well, Stryka is here right beside you. Does that not bring you comfort?" Hippocrates gestured to the one-eyed dragoness, who promptly woke up and purred as the Greek physician stroked her snout.

Zenna smiled a bit. "No, Teacher…I was thinking of my best human friend, Hiccup," she clarified. Hippocrates nodded in understanding. It had been exactly two years and six months since Zenna joined his school. And two years and six months since she last saw her family and friends. Over the course of two years and six months, a bond between teacher and student had been formed and Hippocrates came to know of Berk and of the Vikings and dragons that resided there. Zenna had initially struggled to fit in with the boys learning the healing arts and talking about her life on Berk made her feel at ease during her first few months on Kos.

Hippocrates had been slightly amused when he learned about Hiccup, Zenna's runt of a friend, and had received quite a frightening glare from his Nordic student when he had laughed at the name. His students who had also mocked Hiccup also received that glare, which could have made Cerberus whimper like a common, frightened dog. Truly, Zenna was close to the boy and would not tolerate, even in foreign countries, anyone making fun of him.

"I miss him, Teacher…" Zenna admitted, sighing sadly. "Have you written him a letter?" Hippocrates asked her. Zenna shook her head and pulled out a piece of parchment with the Berk crest stamped on it. "He wrote me a letter two weeks ago. I've been reading his letter again and again for the past few days…But it just makes me miss him more…" she sighed.

Hippocrates smiled and gently patted her head. "Why not write to Hiccup, Zenna? And I mean really write. Pour out your heart into the words you put on paper. Perhaps it will make you feel better," he advised. Zenna instantly grinned. "Thank you, Teacher!" she said gratefully before leaving the gardens, Stryka right on her heels.

Back in her room in the house where she and Stryka lived with a Greek family, Zenna took out her quill pen, dipped it into an inkwell and put it to the paper she had prepared, along with a stack of them, and wrote and wrote and wrote and wrote. She poured out her whole heart and soul into the words she wrote, revising and editing her letter several times. Crumpled paper littered the floor as she wrote like her life depended on it.

Finally after going over her letter several times to make sure it was well written and neat, Zenna placed it in an envelope and sealed it. With Stryka she headed out to the docks. She was lucky to see Trader Johann again. After exchanging pleasantries with the trader, Zenna gave him the letter along with payment of a few gold pieces.

"Please deliver it to Hiccup as soon as possible, Johann," Zenna requested politely. "Consider this letter to Master Hiccup delivered, Lady Zenna," Trader Johann laughed before sailing away.

'I hope he gets it soon…' Zenna thought hopefully as she and Stryka went back to the school so she could study for her next test.

Exactly 14 days and 23 hours later, two siblings not by blood but by bond received their letters.

Hiccup's letter to Zenna will be on the next chapter ;)