Before the time of chakra Susanno pranked Amateratsu and Tsukuyomi. Of course it didn't go as expected and they were forced in human form, searching for each other, not remembering their godly lives. At first Susanno thought that they would return to the god realm once their human bodies died but he was wrong. That led most of the other gods to panic. It was Shinigami who realised and pointed out that they would return only once they found each other.
Generations after the catastrophic prank the Rikudou Sennin had two sons from two different women. One with an aura of fire and ozone and one with a spring aura. The children were Indra and Ashura. And Indra's mother was a reincarnation of Amateratsu and she just like everyone else before her stared at the moon and wished for the reincarnation of Tsukuyomi to find her, the gods having shared the knowledge about what happened to the couple.
So it wasn't all that big of a surprise when Uchiha Tajima's first born and most talented son started staring at the full moon at the age of 10, wishing to be seen by the celestial body.
„You seem distracted." Said Tobirama to Madara but he got no reply from the man.
„Don't pay him much mind." Started Izuna knowingly, „It is full moon tonight and it seems that Tsukuyomi-sama's creation is up early too." And finishes with a pointed look at the albino as if to say to say he was stupid which earned him a raised eyebrow and a what-are-you-not-telling-me look.
He wasn't one much to judge either way. After all he had the urge to search for something he didn't know he needed since he was 8 years old during the full moon. The only reason he isn't running around like dog which has lost its toy is because the resistance to the temptation had been beaten into him from young age.
The Senju-Uchiha brothers, Hashirama, Madara, Tobirama and Izuna, were in an office which has yet to be filled with people for only the founding clans live in Konoha with only one of them being distracted from his work and another barely able to be productive.
„You seem twitchier than usual... Is it because of the full moon?" Izuna hummed to Tobirama.
„You are imagining things." Replied the albino.
„Aww man. And here I hoped that it is you who Aniki is waiting for." Whined the younger of the Uchiha brothers.
„What are you talking about Izuna?" questioned the Senju clan head.
„Before the time of chakra Susanno pranked Amateratsu and Tsukuyomi. That didn't end with the expected laughter but with the couple send to the mortal realm without a memory of their godhood. They could still feel each other and on some level they knew there was a person they needed but didn't know who that person was. The one who held the soul of Amateratsu gazed upon the moon and that left Tsukuyomi restless, in need to find the owner of the eyes. They are bound to the mortal realm, resurrecting and transmigrating until they find each other. Those are the words of the Amatsuhikone-sama." Explained Madara absentmindedly as if he was recitating a poem he learned long ago without lifting his eyes from the moon.
„I have never heard of that..." Stated Hashirama which earned him an eyeroll from the rest of the occupants of the room without removing their eyes from what they were watching and Tobirama shivered as if warm sunlight had hit the right spot on his neck to warm his body.
Then Tobirama looked at Madara and sighed, „It seems like we won't be doing much more work today so we might as well leave early." Izuna silently agrees while Hashirama sighs in relief. It was Madara and Tobirama who did most of the work with Izuna barely able to keep up, leaving Hashirama to breathe Izuna's dust. That's not to say that Hashirama or Izuna weren't competent, it's just that Izuna isn't all that experienced and Hashirama simply sucks at filling out paperwork.
That was when he noticed that the Uchihas left through the window and his brother hightailed it out of here leaving him all alone to warp things up. At least the Uchihas took care of their respective workspaces. Tobirama took care of his working place before putting his brother's stationary away so that they are useable on the next day.
Tobirama turned in his bed with restless energy and sighed. If what Madara said was true then he ought to find the man and figure out how to proceed from there. He wasn't sure what kind of relationship the older male would want with him, the one who almost killed the only baby brother he has left.
When they returned to the Uchiha compound, Madara promptly settled on the roof of his house, it has always been his favourite place to watch the sky and it won't disappoint tonight as well, while Izuna disappeared in Madara's house only to reappear with a tray filled with onigiri and carrot sticks. Madara nodded in thanks and said, „Tonight the moon feels closer than ever."
Izuna hummed hopefully, „Hopefully that means that Tsukuyomi-sama is nearby, it would be a shame if you are like all the other reincarnations of Amateratsu-sama."
„Indeed." Was the only response Izuna got.
„Well" Izuna started, getting up from the seat he had taken during his short talk with Madara, „I will be back later with some more food and a blanket or two. See ya later." After promising that he left to attend to his own house.
„See ya later otouto." Murmured the elder of the two as if in daze.
Madara barely noticed when he got to his favourite place to watch the moon not did he notice his brother tending to him but he noticed Tobirama approaching him. He was in his sleeping kimono shirt and black pants, 'At least his style is better than his brother's'. Madara thought absentmindedly, feeling the chill of the night despite the blankets Izuna brought to him.
Then the albino entered his direct line of sight and a name left his lips without a thought but truth rang in his voice, „Tsukuyomi."
When the albino heard that, his face twitched, his eyebrows rise and his eyes widened a bit. Not by much but enough to be noticeable. What truly surprised him was that he replied the Uchiha, his lips moved, air left his lungs to tickle his vocal cords and his tongue moved to form the word which left his mouth without his consent, „Amateratsu." And then he brought the still hypnotised Madara and his things in the Uchiha's house. And since then the sun and the moon moved together no matter what. Those who knew why were happy and those who didn't were sadden that they won't see the moon so clearly during the night.
Several centuries later.
„I still can't believe that you didn't know about our legend love." Said a black haired person with a glow strong enough to rival the sun.
„My last mortal family weren't the most religious one." A white haired person replied, his silver glow diminishing in embarrassment.
„You keep telling yourself that love." Laughed the first figure, „You could have always read on it Tobira'." They called teasingly.
„You are probably the only person I let get away with butchering my name Mada'." Murmured the now introduced 'Tobira'.
„Indeed." Replied 'Mada' with a grin.
The two figures were in fact Uchiha Madara and Senju Tobirama, the reincarnations of Amateratsu and Tsukuyomi. After they died together from old age they easily made their way to Tamakahara. There they were greeted by their not so mortal family and remembered all the lifetimes they had ever lived and realised that it was their lifetime as Madara and Tobirama where they had ever met, let alone realise who the other was.
„Would you like to visit Hashirama today? Shinigami is whining about your brother's whining." Murmured Madara.
„I suppose it would be best to visit if only to stop his whining for the next few years." Scowled Tobirama, earning a laugh from Madara.
„To save Shinigami?" Questioned the... diety of the sun.
„Yes."
...
Then they both laughed.
AN: So far so good. Five more to go.