I Woke Up in the Same Bed as My Nemesis

Simply put, this is the story of the Second Hokage, who, on his way back to the Pure Land after the Fourth Great Ninja War, gets dragged into a parallel timeline by another version of himself and forced to take over his life. The first thing he discovers when he opens his eyes is that he's sharing a bed with his nemesis, Uchiha Izuna. If it had happened just once, that would be one thing. His secrets have been found out, but he's sure Izuna won't tell anyone. After all, being tricked by some stranger into rolling around in bed with your mortal enemy is pretty embarrassing. But can someone explain why, ever since that time, Uchiha Izuna, that rabbit-eyed guy, keeps showing up in his bed for a few days every month?! This story is also known as: Every Month, I End Up Sharing a Bed with My Nemesis for a Few Days!

Warnings:

1. The Second Hokage is reborn from the time of the Fourth Great Ninja War.

2. There is OOC characterization in this story, and the characters are allowed to run wild!

3. Tobirama and Hashirama's father don't know that the Second Hokage is intersex. Their mother and the midwife kept it a secret back then.

4. The Second Hokage is intersex in this story. He was intersex in his first life too, which is why he stayed single his whole life.

5. The Second Hokage, being intersex, has periods, but they're never very regular.

6. This story doesn't follow the original plot, and there will be mpreg!

The pairing is Izuna/Tobirama! Yes, to be clear, this is somewhat similar to the Madara/Tobirama story "Destined to Have You" by Chen Shi Zhi Fei. We talked privately, though, so this story has only borrowed the premise.