i'd die for tobirama actually

Tobirama brings all his books and scrolls and lab equipment with him and manages to get Madara to give him a room to set up his lab in. It's not the best because it's still in the main house and his experiments are dangerous at best and deadly at worst so it would be better to have a standalone building but he'll look into that in the future.

They consummate the marriage and Tobirama has no issues about carrying Madara's heir because he likes children and expects to have many of them now that they are no longer at war. The first week Madara isn't sure how to live with Tobirama so he busies himself with clan work and leaves Tobirama to entertain himself at home. Tobirama of course also has no problem with this as he busies himself in his lab and can make his own meals with the ingredients they already have in the kitchen and he doesn't need to communicate with anyone at all. He's living his best married life.

Madara isn't really comfortable with daily living with Tobirama but he has no problem making pups with him and a month later Tobirama confirms that he is pregnant. That is also the time when Madara and the elders start to slowly want to introduce the duties of the Matriarch to Tobirama. When Madara brings the elder who had been handling the Matriarch duties to their home and asks Tobirama to meet, Tobirama is confused.

“elder Yomi is here to talk about the Matriarch duties.” Madara says and Tobirama looks like he understands, “Ah I see. Will she be confirming the pregnancy?”

Madara and the Elder are both confused, what do the duties of the Matriarch have to do with the pregnancy? “No we have no issues with the pregnancy.”

Then now Tobirama is confused, “If not the pregnancy then what else?”

Madara and the Elder then lay out all of the duties that the Omega of the household have to do and it's a very long list of very many many things and Tobirama's scent gets more and more sour as they continue. In the end they have to stop because of how displeased Tobirama is, asking him if there was anything wrong.

“You allow married Omegas to do this?” He's completely baffled and displeased.

The elder and Madara assume something different from his words and get indignant on behalf of their omegas, “Omegas are just as capable as Alphas, you of all people should know this.”

Tobirama doesn't understand their anger and asks them to calm down, “Of course Omegas are capable, but why would you ask a married Omega to do the duties of an Alpha or unmarried Omega?”

This is the moment they all realise there must be some cultural difference here and they have a lot to work through. So they all settle down to deal with it on the spot.

For the Senju, unmarried Alphas and Omegas have the same responsibilities and same rights, however once an Omega was married they have the choice to either bear children, or choose to continue their previous responsibilities without having children. They can of course choose to do both but it's rare for shinobi Omegas to do so because of the dangers of carrying out missions and never coming home, leaving their pup without a parent. Aside from having pups they are free to do whatever they wish whether it was take up civilian work or just spend their days keeping house, married Omegas are free to choose whatever they wish and nobody is allowed to tell them no.

The Uchiha on the other hand have no such distinction. Whether married or unmarried all Alphas and Omegas have their responsibilities and it doesn't change just because they are married or pregnant. The pregnant omegas will get their time off to care for their young but they are expected to return to work once the pup is able to be passed off to grandparents or the communal child rearing services.

Madara and the elder explain to Tobirama that they expect him to take the duties of the Matriarch like dealing with everything to do with in clan and helping Madara wherever he needs. Madara expected that Tobirama would have no issues with this because he had been so helpful during the peace treaty with drafting things for Hashirama and speaking with everyone, Madara had observed that Tobirama was a very capable Omega hence he was agreeable to the marriage.

Tobirama is absolutely shocked and disgusted. The reason he had agreed to be married was because he has finally achieved his brother's dreams for him, and he thought it was finally time for him to settle down and live the life that he wanted. Which was to have children and spend his days researching and teaching children and dabbling in anything and everything that he wished without having to do things he disliked like talking to others when making plans or being a supervisor to his clan members. He thought that his distasteful days of having to manage unruly clan members and dealing with everyone's jobs for them were over. Hashirama had been happy for him too to finally be able to live as he pleased.

Madara finally understood what he had been questioning at the start of why Tobirama had been so willing and Hashirama so happy at the marriage alliance. Madara tells tobirama that that can't work because the Uchiha don't operate like that and the elder backs him up. Tobirama is extremely unhappy that he is being forced to do things that he as a married Omega should not be doing, and he asks Madara, “Are Uchiha Alphas so incapable that you are unable to care for your married mother Omegas in this way?”

That seems to hit some sort of sore spot for the Alpha's pride, sputtering that this is not about caring for their Omegas, their omegas are well cared for! Because they can care for themselves!

Tobirama doesn't relent, saying if the Alphas are capable then why are you making Omegas who want to be caring for their young do things that would displease them? Wouldn't that point to the Alphas not being capable enough that they need Omegas to do it for them? Is that the kind of clan that Tobirama has married into?

“You are so capable why would you not want to do these things?”

“I am capable yes, but that does not mean I wish to do any of these duties that are so-called required of your Omega mothers.” Tobirama turns his nose up at it.

Tobirama normally would not behave so snobbishly but he has had enough of having to do everyone else's work and he wants his life to be his own now, hell if he would let Uchiha Madara force him to do more work.