The newlyweds have separate bedrooms. Kaen cannot afford to leave the job market for 9+ months, so she hires a surrogate to carry hers and Reijin’s children. Again, Reijin is conflicted, but convinces himself it’s for the best (it’s not like he actually WANTS to go the traditional route with this woman). 

From Kaen’s eggs and Reijin’s sperm, three viable embryos are obtained. The surrogate is successfully implemented with one and produces a daughter - Touka (who has pink hair rather than red going on white, because of my personal preference). The second pregnancy results in a son - Yukio. Touka has a fire quirk while Yukio has an ice quirk. Reijin is happy to have two healthy children. Kaen is initially satisfied with them as well, seeing Touka as her successor. The mother and daughter initially have a very healthy and close relationship. Kaen trains Touka and inspires her to strive for the top hero rank. The little girl idolizes her mother and wishes to be just like her - big, strong and magnificent. Meanwhile Reijin takes greater care of Yukio, passing onto him his love for art and nature. Those are relatively happy times for the young Himura family.

Unfortunately, as Touka gets bolder with her training, it becomes apparent she is susceptible to burns. Medical consults reveal her body is suited for handling extreme coldness rather than extreme heat. The girl thinks she can overcome those limitations by training harder, but her mother has already given up on her. With such a constitution, Touka can only ever be a mediocre fire user. Consumed by her disappointment, Kaen escapes into work, leaving Reijin to deal with the fallout. 

Touka doesn’t understand why her mother doesn’t love her anymore. She continues to experiment with her quirk, deaf to her mother’s scoldings and her father’s pleas. The spouses fight a lot in this period, with Reijin demanding more involvement from Kaen and Kaen arguing she's doing everything she can to discourage Tuka from self-harm, only the stubborn child won’t listen. Amidst this mess it comes to the light that Kaen had gone behind Reijin’s back and had their final embryo implemented into a surrogate as well. The resulting daughter, Natsumi, appears to be a natural ice user. Kaen washes her hands off her family, disappearing for months at a time to fight off crime. 

Finally, Reijin has had enough. He leaves the three children with their grandparents and confronts Kaen in her office. He lays onto her like he never had before. Their eldest is constantly starting fights with other children and teachers. She’s skipping school to train. The younger two children are neglected, because their father has to constantly put down Touka’s fires. If Reijin’s hair wasn’t white to begin with, he’d have gone gray by now. They cannot go on like this. Kaen has to step the fuck up, talk to her kids, and understand she is a part of a family. If he has to drag her ass back home, then so be it!

Surprisingly, Kaen finds this new, ferocious side of her husband, extremely arousing. All the stress of their respective lives pushes them into a wild frenzy, wherein the marriage is, at long last, consummated. 

Afterwards, Kaen agrees to spend more time with her family. With Reijin’s help, she approaches Touka. They discuss ways to help her. If her body is suited for extreme coldness, she could become a hero in the far North. All the surrounding ice would keep her safe from her own flames. People would worship her as the fire bringer. Alternatively, she could train precision rather than raw power. Every fire user can burn a building, but few control their quirk well enough to cauterize a surgical wound. Focusing all the heat in a tiny spot is the way to go. Kaen might be a powder keg, but Touka could become the silent sniper. 

The little girl is stubborn. She sees all those talks as a rejection on her mother’s part. She wants to be the kind of hero Kaen is. Anything else is pitiful. Still, she might have become open to those new opportunities. Might have. If it wasn’t for Kaen’s pregnancy.  

Having briefly considered termination, Kaen chooses to keep the child and takes time off work. While Yukio and Natsumi are happy, Touka is not. Her mother only returned to them for the sake of this new baby. This child, the great hero Endeavor chose to carry herself rather than hire a surrogate. This child she obviously loves the most of all. So Touka hates the new sibling from the get go. 

The new baby, Shinka, is the successor Kaen has always dreamed of. The child with both the fire and ice quirks. The perfect heir. The one who could become the greatest hero of them all. The idea excites her so much she once again forgets about her remaining children. 

Reijin is conflicted. He knew this would happen. He knew this new baby would disturb the peace he and Kaen had only started to rebuild. He knew it would have been better for the children they already had if she terminated the pregnancy. Still, he couldn’t bring himself to push for it. HE didn’t want to be responsible for the death of a child. Thus he had traded his own peace of mind for his family’s stability. He is as much to blame as his wife is. And he shall spend the rest of his life repenting for it. 

Reijin and Kaen divorce. He takes the three older children far North. They can start anew, away from the toxic influence of that horrible woman.