At the start of the world, the sun’s light got weaker and weaker. The god of the sun, Katsuki, was worried that the sun’s light would die out, leaving the people of the earth below in darkness. So he had an idea.
He took a bit of the sun’s light in his hands and squished it until it became a small seed lying in his palms. Then, he looked out onto the earth and found a farmer with a small plot of land. Katsuki dropped the seed down to earth and, when the farmer found it, he said, “That seed will bloom into flowers that will replenish the sun’s light. I’m counting on you…”
Getting that the sun god was asking for his name, the farmer replied, rather shakily, “Izu-Izuku!” Katsuki grinned before disappearing into the clouds once more, saying, “Don’t let me down, Izuku.”
Every day, Katsuki kept watch of the little farmer, seeing how he carefully tilled the soil and planted the sun-flower seed, how he toddled out to the sprout every morning and watered it faithfully. Katsuki felt his heart swell when the first tall stalk opened its yellow petals and faced him. The farmer looked up and smiled, too. Katsuki swore he could see it from up in the clouds.
When Izuku was done harvesting the seeds from the sun-flower, Katsuki sent some sparrows down to collect the flower. When put into the flickering remains of the sun’s light, the sun-flower disintegrated with less than a puff… but the sun’s light remained, stronger than before.
Relieved that it worked, Izuku planted and harvested the sun-flowers in earnest. Soon, he realized that letters would survive the journey to the heavens, and started writing Katsuki, the missives wordier and wordier with every bundle of flowers sent. Katsuki found himself watching the little farmer more than he would like to admit, moving clouds away from the sun’s beams so they would reach the flowers better, making Izuku’s next letter come just a little bit earlier.
Soon, it was clear to Katsuki that he was in love with the little farmer. Every letter had him enamored with Izuku, and no matter how hard he tried, he loved watching how earnestly Izuku worked to keep the sun-flowers growing, healthy, all for Katsuki’s sake. His love was almost too much to bare.
One night, as Katsuki worried about what to do with his newfound love with a mortal, a meteor shower lit up the night sky. Struck with an idea, Katsuki scrambled out and, with nimble feet, hopped from meteor to meteor down to the earth’s surface, leading him to Izuku’s front door.
Struck that the god he had been working and writing to for so long was knocking at his door, Izuku quickly invited Katsuki in. They spent the rest of the night together, talking, laughing, reveling in the reality of being in close proximity. But Katsuki knew it wouldn’t last. The sun needed him.
“Look, Izuku,” Katsuki said, before the sun was due to rise, “The sun shines as bright as it does because of you. Just say the word, and whatever you want will be yours.”
Izuku took a moment to contemplate his answer. “Come down again with the next meteor shower,” Izuku replied slowly, “that’s all I want.” As the sun rose, casting the sky in brilliant oranges and pinks, Katsuki pulled him closed and kissed Izuku before saying, “I would have done that anyways.”
Years passed like this, the letters, the quick moonlit visits to earth, the longing of wanting more than just one night at a time weighing down on both like stones. Katsuki watched as Izuku aged, and never loved him less for it. Izuku never married, just tended to his sun-flowers and sent them to Katsuki like clockwork. The other villagers took over the sun-flower garden after Izuku passed.
Distraught at Izuku’s death, Katsuki let the sun dim for three days, its rays never getting passed the thick clouds that crowded the skies. Knowing how hurt Katsuki was, and of Izuku’s service to him, the other gods agreed that Izuku deserved the gift of immortality, granting him the position of the god of farming and prosperity.
Katsuki and Izuku’s reunion was nothing short of spectacular. Katsuki didn’t let the sun set for three days, he was so happy. Still being separated stung, Katsuki stuck in the heavens and Izuku helping the people down below, but they were never too far away from each other for long.
The sun-flowers still remember their use to the sun god and the touch of the god of prosperity. That’s where they get their meaning, and why the follow the sun’s arc every day.